Abstract
A punch for a rotary press comprises a shaft with a punch tip at a first end of the shaft and a punch head at the second end of the shaft. The punch head further comprises a mirror surface and a cylindrical surface, as well as intermediate region between the mirror surface and cylindrical surface. The mirror surface defining a central recess surrounded by an annular mirror surface section.
Claims
1. A punch for a rotary press comprising: a shaft comprising, a punch tip at a first end of the shaft, and a punch head at a second end of the shaft, the punch head further comprising an annular mirror surface section surrounding a recess, a cylindrical surface, and an intermediate region disposed between the annular mirror surface and cylindrical surface.
2. The punch according to claim 1, wherein the recess further comprises an edge region configured to surround a base region.
3. The punch according to claim 2, wherein the edge region is a conical frustum or a cone.
4. The punch according to claim 2, wherein a tangentially continuous transitional region is disposed between the edge region and the annular mirror surface.
5. The punch according to claim 2, wherein a continuously curved transitional region is disposed between the edge region and the annular mirror surface.
6. The punch according to claim 4, wherein an angle () between a tangent at the tangentially continuous transitional region and the annular mirror surface section is less than 20.
7. The punch according to claim 4, wherein an angle () between a tangent at the tangentially continuous transitional region and the annular mirror surface section is less than 10.
8. The punch according to claim 1, wherein a depth of the recess relative to the annular mirror surface is less than 4 mm.
9. The punch according to claim 1, wherein a depth of the recess relative to the annular mirror surface is less than 1 mm.
10. The punch according to claim 1, wherein a ratio between a depth of the recess to a diameter (d1) of the recess is less than 2.
11. The punch according to claim 1, wherein a ratio between a diameter (d1) of the recess to a diameter of the annular mirror surface is less than 0.8.
12. The punch according to claim 1, wherein an outer contour of the recess is disposed within an envelope circle with a diameter (d1) which is not greater than one-half a diameter (d2) of a region of the shaft adjacent to the punch head.
13. The punch according to claim 1, wherein a contour of the recess is disposed within an envelope cone, or envelope conical frustum, with a taper angle () of at least 140 and a maximum diameter (d1) which is not greater than one-half a diameter (d2) of a region of the shaft adjacent to the punch head.
14. The punch according to claim 1, wherein a height (h) of all wall sections of the recess perpendicular to the annular mirror surface section is less than 1 mm.
15. A rotary press comprising: a rotor configured to be rotated by means of a rotary drive, the rotor comprising an upper punch guide configured to guide upper punches of the rotary press, a lower punch guide configured to guide lower punches of the rotary press, and a die plate disposed between the upper and lower punch guides having a plurality of cavities configured to interact with the upper and lower punches; a filling apparatus configured to add filling material to the plurality of cavities in the die plate; at least one upper pressing apparatus and at least one lower pressing apparatus configured to interact with the upper punches and the lower punches during operation to press the filling material into the plurality of cavities in the die plate; and an ejection apparatus configured to eject pellets generated in the plurality of cavities from the rotary press.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Exemplary embodiments of the invention are explained in greater detail below with reference to figures. The drawing shows schematically in:
[0032] FIG. 1 illustrates a plan view of a rotor of an embodiment of a rotary press;
[0033] FIG. 2 illustrates an enlarged section of a an embodiment of a press punch and a pressure roller of the embodiment of the rotary press shown in FIG. 1;
[0034] FIG. 3 illustrates an isometric view of an embodiment of a punch of the embodiment of the rotary press shown in FIG. 1;
[0035] FIG. 4 illustrates an isometric view of an embodiment of a punch of the embodiment of the rotary press shown in FIG. 1;
[0036] FIG. 5 illustrates a side plan view of the embodiment the punch shown in FIG. 3;
[0037] FIG. 6 illustrates a cross-sectional view along the line C-C of the embodiment of the punch shown in FIG. 5;
[0038] FIG. 7 illustrates a cross-sectional view along the line B-B of the embodiment of the press punch and the pressure roller shown in FIG. 2;
[0039] FIG. 8 illustrates an enlarged cross-sectional view of detail D from FIG. 7;
[0040] FIG. 9 illustrates a cross-sectional view of another embodiment of the punch;
[0041] FIG. 10 illustrates an enlarged cross-sectional view of detail F from FIG. 9 ; and
[0042] FIG. 11 illustrates an enlarged cross-sectional view of detail G from FIG. 9.
[0043] The same reference numbers refer to the same objects in the figures unless indicated otherwise.
DETAILED DESCRIPTION OF THE INVENTION
[0044] The rotary press shown in FIG. 1, in particular the rotary tablet press, comprises a rotor that is rotationally driven by a rotary drive (not shown) with a die plate 10 which has a plurality of cavities 12. The cavities 12 can for example be formed by holes in the die plate 10. Furthermore, the rotor comprises a plurality of upper punches 14 and lower punches 16 that rotate synchronously with the die plate 10. In each case, a pair consisting of an upper punch 14 and lower punch 16 is assigned to a cavity 12. The axial movement of the upper punch 14 and lower punch 16 during the rotation of the rotor is controlled by upper control cam elements 18 and lower control cam elements 20. The rotary press moreover comprises a filling apparatus 22 which has a filling chamber 24. The filling apparatus 22 further comprises a funnel-shaped filling material reservoir 26 which is connected by a feed section 28 to the filling chamber 24. In this manner, the powdered filling material in the present example passes under the force of gravity from the filling material reservoir 26 via the feed section 28 into the filling chamber 24, and passes therefrom via a filling opening provided in the bottom side of the filling chamber 24 into the cavities 12 of the die plate 10, again under the force of gravity.
[0045] As shown in FIG. 1, the rotary press further comprises a pressing station 30. The pressing station 30 comprises a pre-pressing apparatus with an upper pre-pressing roller 32 and a lower pre-pressing roller 34, as well as a main pressing apparatus comprising an upper main pressing roller 36 and a lower main pressing roller 38. As shown, the rotary press further comprises an ejector station 40 with a scraper 42 which supplies the pellets 44, in particular tablets, produced in the rotary press to a pellet discharge 46 for further processing.
[0046] A control apparatus for operating the rotary press is shown with reference number 48. The control apparatus 48 is connected by lines (not shown) to, inter alia, the rotary drive of the rotor.
[0047] FIG. 2 shows an enlarged representation of part of an upper press punch 14 as it interacts with an upper pre-pressing roller 32.
[0048] FIGS. 3-8 show an example and section of an upper punch 14 of the rotary press shown in FIG. 1. The design of the punches 14, 16 of the rotary press will be explained below with reference to an upper punch 14. In this respect, the lower punches 16 in the depicted example are designed identically.
[0049] Referring to FIGS. 2-8, each upper punch 14 has a punch head 50 on an end of a punch shaft 52. In the portrayed example, the punch shaft 52 (FIGS. 3-6, 8) has a punch neck 54 (FIGS. 3-6, 8) with a cross section that is smaller than the remaining punch shaft 52 (FIGS. 3-6, 8) section. A punch tip 56 (FIG. 1) extending into the cavities 12 of the rotary press during operation is formed on the other end of the punch shaft 52 (FIGS. 3-6, 8). Referring to FIG. 1, the punches 14, 16 of the rotary press are designed to be rotationally symmetrical and are guided to freely rotate in the upper, or respectively lower punch guide 58, 60.
[0050] Height lines are depicted on the top side of the punch head 50 in FIGS. 3-5 for the sake of illustration. In the embodiments of FIGS. 3-5, the punch head 50 comprises a cylindrical surface 62 that transitions via a conical intermediate region 64 into the punch neck 54 of the punch shaft 52. On the top side of the punch head 50, there is a annular mirror surface section 66, which is flat. The annular mirror surface section 66 and cylindrical surface 62 are connected to each other by a rounded intermediate region 68. Referring to FIGS. 3-5, the flat, annular mirror surface section 66 borders a recess 70. In the embodiments of FIGS. 3-4, the recess 70 possesses a closed base region 72 and an edge region 74 which terminates in the annular mirror surface section 66 and is configured to be conical, or respectively frustoconical. Referring to FIG. 6, it can be seen that the recess 70 can have a conical shape, or respectively frustoconical shape. As shown in FIGS. 3-4, between the edge region 74 and the annular mirror surface section 66, there can also be a rounded transitional region which in particular can be tangentially continuous or continuously curved relative to the annular mirror surface section 66.
[0051] Referring to FIG. 6, the contour of the recess 70 lies within a cone with a taper angle (opening angle) that is about 140 in the portrayed example. The outer contour of the recess 70 which is formed in the portrayed example by the inner edge of the annular mirror surface section 66 bordering the recess 70 lies on an envelope circle with the diameter d1 (see FIGS. 6 and 8). In FIG. 8, it can also be seen that the punch neck 54 has a diameter d2. In the depicted example, d1=1/2d2. By means of this embodiment, pressures introduced into the punch head during operation, in particular in the region of the edge of the recess 70, can be very evenly introduced in the punch shaft 52, in particular the punch neck 54, while interacting with the upper pre-pressing roller 32 as illustrated in FIG. 8 by the force lines 76. As shown in FIG. 8, the pressure arising during operation is accordingly divided evenly to the left and right of the recess 70 and is homogeneously conducted in the punch shaft. To the extent that d1 is smaller than d2, introduction of pressure in the direction of the shaft axis is increased. This is also not problematic in principle for the stability of the punch 14.
[0052] FIGS. 9-11 show another embodiment of an upper punch 14 which can be used in the rotary press according to FIG. 1. The same correspondingly holds true for the lower punches (not shown).
[0053] The upper punch 14 shown in FIGS. 9-11 differs from the upper punch 14 shown in FIGS. 2-8 only in terms of the geometry of the recess 70. Accordingly, the edge region 74 (FIGS. 10-11) of the recess 70 is curved slightly concavely, and the recess 70 possesses a central hole with a perpendicular cylindrical wall section 80 (FIG. 11) and a base region 72 (FIG. 11). As can be seen in particular in FIG. 10, the recess 70 at the transition to the annular mirror surface section 66 possesses a tangential angle between a tangent 78 placed in this region and the annular mirror surface section 66 of less than 20. A strong edge in the region of the transition is thereby avoided, which otherwise could cause stress peaks and hence the danger of a premature failure of the punch head.
[0054] As can be seen in FIG. 11, the height (h) of the perpendicular cylindrical wall section 80 which is perpendicular relative to the annular mirror surface section 66 is also relatively small; in the present example, less than 1 mm. Such perpendicular wall sections pose in principle a barrier for the introduced force as can be seen with reference to the force lines 76 drawn in FIG. 11. Accordingly, the perpendicular cylindrical wall section 80 causes a necessary deflection of the introduced force which can have a negative effect. Consequently, the height (h), assuming that perpendicular wall sections are provided, should be as small as possible.
[0055] By providing the recesses 70, 70 in the punch heads 50, a more even load on the punch heads 50 and the upper and lower pressing rollers 32, 34, 36, 38 interacting with them is achieved so that the life of the punches 14, 14, 16 is increased without impairing the durability of the punches 14, 14, 16. The wear of the pressing rollers 32, 34, 36, 38 and the rotary press overall is reduced, and the generated noise is reduced.
REFERENCE NUMBER LIST
[0056] 10 Die plate 12 Cavities 14 Upper punch 14 Upper punch 16 Lower punch 18 Upper control cam elements 20 Lower control cam elements 22 Filling apparatus 24 Filling chamber 26 Filling material reservoir 28 Feed section 30 Pressure station 32 Upper pre-pressing roller 34 Lower pre-pressing roller 36 Upper main pressing roller 38 Lower main pressing roller 40 Ejector station 42 Scraper 44 Pellets 46 Pellet discharge 48 Control apparatus
[0057] Punch head Punch shaft Punch neck Punch tip Upper punch guide Lower punch guide Cylindrical surface Conical intermediate region Annular mirror surface section Intermediate region Recess 70 Recess Base region 72 Base region Edge region 74 Edge region Force lines Tangent Perpendicular cylindrical wall section
