Compression punch for a rotary press

Abstract

A compression punch for a rotary press, with a shaft, a punch head disposed at one shaft end and a compression zone disposed at the other shaft end, wherein the punch head features an upper mirror surface, an outer cylinder surface and a curved transition zone between the mirror surface and the cylinder surface, wherein the mirror surface and the transition zone form a three-dimensional surface, whose course in at least one radial direction can be described by a mathematical function whose second derivative is continuous.

Claims

1. A compression punch for a rotary press, with a shaft (12), a punch head (14) disposed at one shaft end and a compression zone disposed at the other shaft end, wherein the punch head (14) features an upper mirror surface (16), an outer cylinder surface (18) and a curved transition zone (20) between the mirror surface (16) and the cylinder surface (18), characterized in that the mirror surface (16) and the transition zone (20) form a three-dimensional surface, whose course in at least one radial direction can be described by a mathematical function (30) whose second derivative is continuous, and further characterized in that the radius of curvature of the three-dimensional surface decreases continuously in the radial direction from the mirror surface (16) to the cylinder surface (18).

2. A compression punch according to claim 1, characterized in that the course of the surface in an arbitrary radial direction is described by the mathematical function (30).

3. A compression punch according to claim 2, characterized in that the punch head (14) is rotationally symmetric.

4. A compression punch according to claim 1, characterized in that a zone (22) rounded with at least a given radius is provided between the transition zone (20) and the cylinder surface (18).

5. A compression punch according to claim 1, characterized in that the punch head (14) features a convex transition zone (24) from the cylinder surface (18) towards the shaft (12).

6. A rotary press with a rotor which has an upper and a lower punch guiding device, in each of which a plurality of compression punches (10) according to claim 1 are guided, which co-operate with bores of a die plate that is arranged between the upper and the lower punch guiding device, wherein the punches (10) are axially movable in guide bores of the punch guiding devices, and their punch heads (14) co-operate with compression rollers of the rotary press in order to compress powder-shaped material in the die bores.

7. A compression punch for a rotary press, with a shaft (12), a punch head (14) disposed at one shaft end and a compression zone disposed at the other shaft end, wherein the punch head (14) features an upper mirror surface (16), an outer cylinder surface (18) and a curved transition zone (20) between the mirror surface (16) and the cylinder surface (18), characterized in that the mirror surface (16) and the transition zone (20) form a three-dimensional surface, whose course in at least one radial direction can be described by a mathematical function (30) whose second derivative is continuous, and further characterized in that the radius of curvature of the three-dimensional surface decreases continuously in the radial direction from the mirror surface (16) to the cylinder surface (18), and further characterized in that at least one edge is provided between the transition zone (20) and the cylinder surface (18).

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) An example of the present invention's realisation will be explained in more detail by means of a drawing in the following.

(2) FIG. 1 shows schematically a compression punch of the present invention in a partial side view, and

(3) FIG. 2 shows schematically a diagram for the illustration of mathematical functions.

DETAILED DESCRIPTION OF THE INVENTION

(4) While this invention may be embodied in many different forms, there are described in detail herein a specific preferred embodiment of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiment illustrated.

(5) As far as not indicated otherwise, same reference signs designate same objects in the figures. A cut-out of a compression punch 10 of the present invention is shown in a side view in FIG. 1. The upper end of the shaft 12 of the compressions punch 10 is shown with the punch head 14. A per se known compression region is provided at the not shown opposing end of the shaft 12, which co-operates with suitable die bores for compressing powder-shaped tablet material when the compression punch 10 is installed in a rotary press. The punch head 14 is rotationally symmetric, the rotational symmetry axis being shown in dashed lines at the reference sign 15. The punch head 14 has a mirror surface 16 that is flat at the upper side and circular in the top view. Besides, it has an outer cylinder surface 18. Between the cylinder surface 18 and the mirror surface 16, there is a curved transition zone 20. In the shown example, the mirror surface 16 and the transition zone 20 form a three-dimensional curved surface, whose course in an arbitrary radial direction of the punch head 14 is described by a mathematical function that is continuous in its second derivative. In particular, the radius of curvature of the three-dimensional surface decreases continuously towards the outside in the shown example, starting from the centre of the mirror surface 16. The height of the punch head 14 decreases also continuously, starting from the mirror surface 16 and towards the cylinder surface 18. Between the transition zone 20 and the cylinder surface 18, a zone 22 rounded with a given radius is provided. A convex transition zone 24, globular in the example, is provided at the lower side of the punch head 14 between the cylinder surface 18 and the shaft 12, which verges into the cylinder surface 18 via a first rounded zone 26 and verges into the shaft via a second rounded zone 28.

(6) In FIG. 2, a mathematical function f(x) is shown at reference sign 30, which depicts the two-dimensional course of the transition zone 20 up to the mirror surface 16 in an arbitrary radial direction. It is dealt with a polynomial function of the following kind:
ƒ(x)=a.Math.x.sup.3−b.Math.x.sup.2+c.Math.x,
wherein a, b and c are suitable constants whose value is determined depending on the desired geometrical shape of the punch head.

(7) Above the values of the x-axis shown in FIG. 2, the function 30 may then be defined as being constant e.g., so that it maps the plane mirror surface. It must be noticed that in FIG. 2, the zero point of the coordinates was set to the lower edge of the three-dimensional surface formed by the transition zone 20 and the mirror surface 16. Thus, the y-axis represents the height of the punch head 14. In a rotation around a suitable axis, the function 30 shown in FIG. 2 correspondingly expands the three-dimensional surface formed by the transition zone 20 and the mirror surface 16. The first derivative f′(x) of the function f(x) is furthermore represented in dashed lines at reference sign 32 in the diagram in FIG. 2. Finally, the second derivative f″(x) of the function f(x) is represented in dashed lines at reference sign 34 in FIG. 2. It can be recognised that the second derivative f″(x) of the function f(x) is continuous.

(8) The compression punch according to the present invention shown in FIG. 1 alleviates the noise emissions that occur in the contact with the compression rollers, as well as the wear of the punch head and the compression rollers when it is operated in a rotary press. Moreover, the very flat transition of the transition zone 20 into the mirror surface 16 results in an increased pressure hold time of the punches, so that even materials that are difficult to compress can be processed without problems.

(9) The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.

(10) Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.

(11) This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.