Patent Application
20050274251
This application claims the priority of German Patent Application No. 20 2004 009 138.0, filed on Jun. 9, 2004, the subject matter of which, in its entirety, is incorporated herein by reference.
The invention relates to a punching device and its punching die. In particular, the invention relates to a punching device and a punching die for unfired sheetlike ceramic substrates, in particular so-called green sheets.
Green sheets must as a rule, in their production, be provided with a number of small holes that are later used for through-contacting conductors that are mounted on the ceramic substrates. These are relatively small holes, of markedly less than one millimeter in diameter, and such holes must be made in large numbers. The punching device has a correspondingly large number of punching dies. The punching dies are provided with heads that are held in a holding device, such as a holder plate, in order to be moved with it in the longitudinal direction of the shaft, or in other words for instance up and down.
A similar punching device is known for instance from European Patent Disclosure EP 0 354 152 B1. The punching dies here are driven by magnet drives. These punching dies are likewise provided with a head that is mounted on the elongated shaft of the punching die.
In performing their job, the punching dies are exposed to a severe abrasive stress. They must therefore be made of a suitable wear-resistant hard material. They are therefore made of an elongated, needle-like body, on which the head, typically of a different material, for engagement by the head plate or other drive mechanisms, is attached later.
As known for instance from U.S. Pat. No. 3,974,728, the working part of a punching die may also be inserted into a body provided with a head and secured to this body for instance by adhesive. However, this makes production relatively complicated. Since punching dies are considered to be wearing parts, it must be attempted to be able to produce them as fast, simply and inexpensively as possible, yet without sacrificing quality. Quality, however, is definitively determined by the straightness or in other words precision of the punching die. Adhesive points between a cylindrical driving body and a cylindrical working part are critical here.
From U.S. Pat. No. 4,700,601, it is also known for punching dies that are intended for punching paper to be provided with a plastic head. To that end, the metal punching die has an annular groove. The region provided with the annular groove is then sheathed with an extruded cylindrical plastic body, whereupon the plastic partly flows into the annular groove and thus makes a positive-engagement connection between the head and the die.
As a rule, the punching dies for green sheets cannot be provided with plastic heads. Because of the small diameter of the shafts of the punching dies, as a rule adequately durable positive-engagement connections are not obtained between a plastic head and the punching die.
With this as the point of departure, it is the object of the invention to create a punching die for a green sheet punching device as well as to create a corresponding punching device; the punching dies should be simple and economical to produce and should meet high standards for quality.
This object is attained with the punching die of claim 1 and the punching device of claim 20:
The punching die of the invention has a die shaft, which has a head on one end and a working part on the opposite end. On the head end, the die shaft is provided with at least one recess on its jacket face. An annular head is seated in the region of the recess and has a protrusion that engages the recess and thereby secures the head on the shaft by positive engagement. This protrusion is created by plastic deformation of the head. The consequence as a rule is that the material of the head rests with a certain prestressing on the shaft. This is particularly true if the head is made from a suitable metal, such as steel, brass, or aluminum. Unlike an extruded plastic sheath, which can already loosen somewhat as a consequence of natural shrinkage or volatility of the plastic, a firm seat is assured here.
Producing the punching die can be done with very short cycle times. A head blank need merely be slipped over the shaft and then secured on the shaft by a suitable deformation process for the plastic deformation of the head. The production processes with which this can be achieved are for example embossing, pressing, rolling, hammering, or other methods for non-metal-cutting shaping. If the head is of a metal with a low melting point, it could if necessary also be produced by a casting process, such as diecasting. However, this is considered to be less advantageous, because the effort involved is greater.
The protrusion that secures the head to the shaft is created, as noted, preferably by plastic deformation of the head blank. To that end, an indentation is embodied on the head in production. The shape of the indentation preferably corresponds to the shape of the recess provided on the shaft. If the recess is an annular bead, for instance, then an annular indentation is embodied on the otherwise cylindrical outer circumferential surface of the head. As a result, the requisite plastic deformation of the head is kept to a minimum. However, it is also possible to provide a supplementary counterholding or deforming pressure, for example in the axial direction against the head, in order to promote the radially inward-oriented inflow of head material into the recess of the shaft.
The recess of the shaft preferably has a waistlike shape. Sharp edges are avoided, in order not to favor breaking off of the slender shaft in the region of the recess. The recess is preferably defined by a concave annular face which is embodied without edges or shoulders. The indentation then has a suitably adapted shape.
The head is preferably seated on the end of the shaft that is diametrically opposite the working part. It is preferably seated on the end of the shaft, so that the shaft end is flush with the head or protrudes slightly out of the head. It has proved advantageous for the recess and correspondingly the protrusion of the head that engages the recess to be disposed near the shaft end. The opening in the head, on the side facing away from the shaft end, thus has a cylindrical guide portion, which transmits tilting moments that engage the head to the shaft or is braced on the shaft without stressing the zone of the shaft that is weakened by the recess. This is particularly applicable if the recess in the shaft, as is preferably the case, is flush with the upper plane face, oriented toward the shaft end, of the head.
Before its plastic deformation, the head preferably has a through bore whose width is somewhat greater than that of the shaft, so that the shaft can be introduced into the head with slight play. After the plastic deformation, the head is seated without play on the shaft. The through bore in the head has preferably been narrowed over its entire length enough that the head is seated without gaps on the shaft.
Besides securing the head to the shaft by positive engagement, connecting it by material engagement may also be provided. This may for instance be an adhesive connection or bond. The advantage of this provision is for instance the ease of introducing the adhesive, which can be accommodated in the recess of the shaft before the plastic deformation operation.
It is also possible for the adhesive, for positively securing the head to the shaft, to be introduced after the plastic deformation of the head, in that after it is applied the adhesive is drawn in between the shaft and the head by capillary action.
In a departure from the embodiments described above, instead of one recess a plurality of recesses may also be provided, and then the above remarks apply accordingly. The recesses may extend around the entire circumference of the shaft or only over a portion thereof and may be axially spaced apart from one another or located at the same height.
Further advantageous details of embodiments of the invention are the subject of the drawings, description, and/or claims.
Exemplary embodiments of the invention are shown in the drawings. Shown are:
In
The upper tool 3 along with the holding-down plate 9 are seen in
The die 8 is axially guided in the holding-down plate 9 by at least one guide bush 13 and optionally by a further guide bush 14 provided on the holding-down plate 9. The die 8, on its lower part, protruding into the guide bush 14, preferably has both a profile which is graduated multiple times and a slender working part 15. Associated with this working part is the punched hole 7, which is embodied in a bush 16 held in the receptacle device 6.
The punching die 8 is held axially nondisplaceably in an upper holding device 17, which serves to impart the axial motion to the die 8. The holding device 17 is part of the upper tool 3. In principle, it may be embodied in various ways. What is essential is that it has a drive element 18, which in the present exemplary embodiment is embodied as a plate and serves to move the die 8 downward. A retriever element 19 also belongs to the holding device 17 and in the present exemplary embodiment is embodied as a plate and serves to move the die 8 counter to its punching direction, that is, away from the receptacle device 6. The plates that form the drive element 18 and the retriever element 19 may be embodied as resting firmly against one another, as shown, or they may be embodied as movable counter to one another. They may be tensed against one another by spring means and firmly clamp the die 8 between them. Spring means, not shown, may also be provided between the die 8 and the holding device 17.
The punching die 8 has at least one preferably cylindrical elongated shaft 21 and one likewise preferably cylindrical head 22, which are joined to one another by positive engagement. The shaft 21 and the head 22 preferably comprise different metals. The shaft 21 is optimized with regard to its punching properties. In particular at its working part 15, it is subject to not inconsiderable wear, particularly in the region of its cutting edges. This potential problem is addressed by means of a suitable choice of material. Hence the shaft 21 comprises a suitable steel. The head 22, conversely, serves merely to introduce the requisite driving forces into the die 8. Excessive hardness or wear resistance is not critical here. Hence it is made as a separate part from a suitable metal, such as a readily deformable steel, or other metals, and secured to the shaft 21. This is illustrated in detail in
The head 22 is embodied of an initially hollow-cylindrical blank 22′, which has a central through bore 25. The diameter of the through bore is preferably somewhat greater than the diameter of the shaft, so that the blank 22′ can be slipped over the shaft 21 without difficulties. For securing the blank 22′ to the shaft 21 and thus for embodying the head 22, the blank 22′ is deformed. This can be seen by comparing
The configuration presented here has the advantage that the head 22 can be mounted on the shaft 21 in an axially desired and selected position. The precision of the location of the recess 23 does not play a role. The position of the head 22 is defined at the moment when the head 22 is compressed. Other production tolerances play only a very subordinate role, if any. High-quality punching dies 8 can thus be produced in a simple way. Moreover, the most various embodiments can be created in the simplest possible way; for instance, variously shaped heads 22 can be combined with shafts 21 of one and the same type. Different axial head lengths or head diameters or head materials may be employed. Moreover, the heads 22 may be secured in various axial positions, in which the recess 23 is located inside the through bore 25. It is furthermore possible to make the recesses 23 at different positions along the shaft. This is particularly true if the indentations are created by a metal-cutting machining operation, such as grinding.
The punching die 8 described thus far functions in the punching tool 1 as follows:
As shown in
For the die 8 of
The recess 23 does not extend over the entire circumference of the shaft 21, but rather only over part of it. They may be presented in the form of a rounded notch that for instance follows along a cylindrical jacket face. Optionally, on the diametrically opposite side and at the same height, or axially offset as shown, a further recess 35 may be provided, which has the same shape or a modified shape. Correspondingly, the head 22, after deformation of the blank 22′, has a first, upper indentation 27 in the region of the upper recess 23 and an indentation 36 in the region of the lower recess 35. The indentations 27, 36 are created by radial compression and deformation of the blank 22′ and form dents or impressions in the jacket face 26.
As
The punching die of the invention has a head 22 held by positive engagement. The head 22 is held on the shaft 21 of the die 8 in that by means of plastic deformation, for instance by radial application of pressure, material is positively displaced radially inward, so that a protrusion 28 is embodied which rests over a large area on the wall of a recess 23. A more secure, more durable force transition is assured.
It will be appreciated that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2004 009 138.0 | Jun 2004 | DE | national |
