Patent Application
20140079582
The invention relates to a lattice part made of metal, to its use, and to a method of producing a lattice part of metal.
Furthermore, the invention encompasses a method for the production of a lattice part made of metal or of a metal alloy comprising a metallic node bond of the lattice members, the lattice having a thickness of less than 1 mm with a magnitude of the opening surfaces of less than 50 mm2.
Coarse lattice parts made of metal, which have large opening surfaces and a considerable thickness of the lattice members are, in most cases, produced by casting a liquid metal into molds, e.g. into sand molds, by open sand casting or mold casting. It is also known to cut out the opening surfaces from a thick metal sheet, which has to be associated to the prior art for providing heavy lattices.
For the production of fine, planar metallic lattice parts, casting methods, in most cases, cannot be applied, because quality deficiencies in castings, such as material discontinuities, lack of formation of nodes and the like, are often inevitable. For these reasons, lattices, which should have thin members and small opening surfaces, in most cases are produced as a wire mesh.
A fine wire mesh with small opening surfaces has mostly equally shaped narrow mesh widths, because the thickness of the wires in the mesh determine and fix the mutual distance with alternately positioning them at the surface.
In diagonal direction of a lattice or under an angle of about 45°, a wire lattice part, and particularly without fixing of the ends of the parts, may easily be displaced and returned within large limits, because no substantial plastic deformation of the material of the lattice wires is necessary and takes place.
In order to stabilize fine lattices, even with a stress by forces in diagonal direction relative to the layers of wires, one has already attempted to interconnect or bond the places of contact of the lattice members at the nodes by welding or by soldering. Although such an interconnection of the lattice nodes is, in principle, possible, it requires, however, additional expenses.
Moreover, lightweight lattices having a thin wall thickness and an enlarged mesh size and opening surfaces entrain problems with respect to stability of the parts, to a uniform and equal spacing of the members or wires from one another and to a uniform dimension of intermediate surfaces.
Wire lattice parts having a low weight are and with a required fineness of their geometrical shape, particularly with a small ratio of the thickness of the members to the open mesh width, therefore, are inapt to reach the properties in use for a desired profile of requirements.
In this respect, the invention is intended to eliminate the shortcomings, and it has the object to provide a lattice part made of metal, which has a great freedom regarding its shaping as well as the creation of the properties in use, and which does substantially not permit a large diagonal displacement of the lattice that can be formed back, but is plastically deformable and has an accurate, fine dimensioning.
A further object of the invention is to specify a method for the production of a lattice part made of metal of the type described at the outset, by which the part has a desired profile of properties, preferably for the use as a stent or as a stent-like system and as an endoprostesis for the use in the human medical and veterinary medical field.
This object is achieved according to the invention in that the lattice comprises a node bond, consists of metal or of a metal alloy, has a thickness of less than 1 mm with a magnitude of the opening surfaces of less than 50 mm2 and that the lattice members and the lattice nodes have the same thicknesses perpendicularly to the lattice surface.
The advantages achieved by the invention consist in particular in that a node bond of the lattice confers to it an improved stability in diagonal direction with respect to the members, and with a formation of light metal results in light weights of the parts. In an advantageous manner, such planar lattices of a small thickness with desired large opening surfaces may present mechanical properties, by which the possibility of use for new applications having a special profile of requirements is made possible.
In one embodiment, the lattice consists of a basis alloy of magnesium, which contains in percent by weight:
In accordance with the invention, an application in vivo of lattice parts within and on the body of men and animals is thereby favorable.
Geometrically, but also in view of a stable expansion of the lattice part, optionally locally over the axis, it may be favorable, if the part has a tubular shape, particularly an undivided tubular shape. In such a manner, high stability of the part is achieved with a small weight of the part.
If the lattice, in a preferred embodiment according to the invention, is produced by casting metal in accordance with DIN 8580, any diagonal displacement of the lattice members can be prevented without any lasting deformation at the nodes, thus favorizing lasting shaping of the lattice surface. In such a manner, three-dimensional lattice surfaces, e.g. partially expanded lattice tubes, may be produced in accordance with the desired profile of properties.
Furthermore, it is particularly advantageous for tubular lattice parts, if the lattice members have an angle unequal to 90° or unequal to 0° in relation to the tube axis, and have in particular an angle of about 45°. In such a manner, when expanding the lattice members, the lattice members are torsion-deformed, substantially in a lasting manner so that stretching or an elongation of members, and thus the risk of breakage, are minimized.
If at least one of the lattice surfaces is machined, a very small lattice thickness can be produced, even with casting a metal lattice, so that economic, process engineering advantages are obtained and also in view of quality, and the lattice properties have likewise a desired stability.
Moreover, a fine lattice tube has advantageously a wall thickness of more than 0.1 mm, but smaller than 0.4 mm, and a diameter of more than 1 mm, but smaller than 4 mm. For such a lattice, important opportunities are given in a technical field of application, but also in the medical field, particularly for the endoprosthetic care of men and animals.
In accordance with an added feature of the invention, at least one lattice surface is a machined lattice surface.
In accordance with an added feature of the invention, the lattice is formed in a tubular shape with a tube axis and said lattice members have an angle unequal to 90° or unequal to 0° in relation to said tube axis. In accordance with a feature of the invention, the lattice members enclose an angle of substantially 45° with the tube axis.
In accordance with an added feature of the invention, the lattice is a lattice tube with a wall thickness of more than 0.1 mm and less than 0.4 mm, and a diameter of more than 1 mm and less than 4 mm.
In accordance with an added feature of the invention, the lattice is a plastically deformable lattice.
In accordance with an added feature of the invention, the lattice is a lattice tube with a non-elastically expandable diameter.
In accordance with an added feature of the invention, the lattice part is formed as a stent or as a stent-like system and as an endoprostesis for use in human medical and veterinary medical fields.
If the lattice, as according to a preferred embodiment, is plastically deformable, in particular if a lattice tube can be expanded in diameter in a lasting way, and if the lattice material consists of a basis alloy of magnesium, as mentioned above, the part may be used in a favorable manner as a stent or as a stent-like system and as an endoprostesis for the use in the human medical and veterinary medical field, particularly in blood vessels of men and animals. In this case, body liquids, slowly dissolve at least the surface region of the metallic stent, while forming calcium hydroxyl apatite, a cartilaginous mass, which is able to take over excellent supporting functions.
The further object of the invention to provide a method for the production of a lattice part made of a light metal or of a light metal alloy comprising a metallic node bond of the lattice members, the lattice having a thickness of less than 1 mm with a magnitude of the opening surfaces of less than 50 mm2 is achieved in that the lattice is produced by casting according to DIN 8680, wherein
There is a variety of advantages of the method according to the invention, and shall be seen or reside in the achievement of favorable lattice properties in an advantageous manner of production and in a high efficiency. Casting the fine lattice of metal insures a desired stability of the lattice nodes as well as the properties, which are preferred in use. In this particular case of casting, it has shown to be advantageous, if in a first step at least part of the mold is formed, because in this way high flexibility of the production method is reached. After jointing the mold, which comprises also supporting it for introducing the metal under pressure, in a second step introducing the starting material in to the cavity of the mold, wherein a flowable metal, which includes solidified particles, may advantageously used.
According to another variant of the method, metal may be applied onto a mold part, manufactured as has previously been explained, in accordance with the liquid or semi-liquid metal spray method and can be solidified. In the subsequent third step, the part can optionally be removed from the mold or can be released from the mold in part only, one mold part having a supporting function, e.g. for machining the lattice. In the last step, finishing of the metallic lattice part is effected, which ensures the intended shape for use and quality.
If in the first step of the production method, at least part of the mold is formed by Powder Injection Molding (PIM), a particularly exact mold shaping can be achieved.
When doing this, it may be favorable, if that mold part, which has been produced in the first step by Powder Injection Molding (PIM), is produced making a mold material by mixing powder, such as ceramic powder, and a binding agent, granulating the mold material and injection molding the granules into a mold, thus forming a green body which can be further made into a brown body, which by sintering can be made to a mold part, preferably having a porosity of 75 to 95% by volume.
In such a way, it is not only the strength of the mold or the mold material which is influenced in a favorable manner, but mold release of a molded part is promoted too.
In view of a particularly high quality of the lattice members, and in particular of the lattice nodes, but also in view of weight and usefulness, it has shown to be advantageous, if a basis alloy of magnesium is used as a light metal, which contains in percent by weight:
If, in the second step, at least partially liquid metal is introduced into the mold cavity, particularly by die casting, shrinkage can be reduced in a favorable manner during solidification of the metal, and the micro-structure of the lattice part can advantageously be made finer.
It is also possible, and it can be advantageous for certain types of production of a lattice part, if, in the second step, a starting material of metal powder and of a binding agent is introduced in to the mold cavity, particularly by injection molding or by Metal Injection Molding (MIM), while in the fourth step of the production, finishing is effected by dense-sintering.
For producing particularly fine and thin lattice parts, which do not exhibit sufficient shaping strength to be machined, the part, in the third step, may be partially released out of or from the mold in such a manner, that it is left on a portion of the mold, thus being supported by it, after which, in the fourth step, finishing of the metallic lattice part is effected by machining for producing the desired exact dimensions, and by subsequent removal of the supporting mold portion, particularly by washing it out or by chemically dissolving it.
Subsequently, a possible production of a lattice part according to the invention shall be explained in accordance with the invention, wherein graphical plots may serve as an aid.
By Powder Injection Molding (PIM), a core part 1 according to
After machining the outer surface of the cast body 4 on the supporting core part 1, a lattice part 5 is produced on it, as is represented in
As shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| A259/2007 | Feb 2007 | AT | national |
This application is a continuation of copending patent application Ser. No. 13/470,783, filed May 14, 2012, which was a continuation of patent application Ser. No. 12/527,781; which, in turn, was a §371 of international patent application No. PCT/AT2008/000048, filed Feb. 12, 2008; the application also claims the priority, under 35 U.S.C. §119, of Austrian patent application No. A 259/2007, filed Feb. 19, 2007; the prior applications are herewith incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13470783 | May 2012 | US |
| Child | 14084218 | US | |
| Parent | 12527781 | Nov 2009 | US |
| Child | 13470783 | US |
