PUNCH FOR PRODUCING HOLES IN THE WALL OF HOLLOW PARTS SUBJECTED TO THE ACTION OF INTERNAL HIGH-PRESSURE

POINCON PERMETTANT DE PERFORER LA PAROI DE COMPOSANTS CREUX ALIMENTES EN HAUTE PRESSION INTERNE

English Abstract

The invention concerns the design of punches for producing holes in the walls
of hollow parts, whereby the part, during punching, is subjected to the action
of a high pressure by a medium. Particularly when producing hollow parts in an
internal high-pressure shaping process, it is common, after the shaping and
when the part is still located inside the shaping tool, to place holes in the
wall. In order to prevent a drop in the internal high-pressure when cutting
through the wall of the part, the punch (1) is, in its area penetrating the
part (2), provided with a shape that is diagonally tapered toward the cutting
edge (3). This effects a sealing during punching.

French Abstract

L'invention concerne la conception d'un poinçon permettant de réaliser des perforations dans les parois de composants creux. Lors de la perforation, l'intérieur du composant creux est alimenté en haute pression par un agent. Notamment lors de la production de composants creux selon le procédé de façonnage par haute pression interne, il est usuel de réaliser des perforations dans la paroi consécutivement au façonnage et lorsque le composant se trouve encore dans le moule de façonnage. Pour éviter une chute de la haute pression interne lors de la séparation de la paroi du composant, le poinçon (1) se distingue par la forme de la zone qui pénètre dans le composant (2), cette forme étant effilée coniquement jusqu'à l'arête de coupe (3). Cela permet d'obtenir une étanchéification de la perforation lors de la perforation.

Claims

- 4 -
claims
1. A punch for producing holes in the wall of hollow
parts subjected to the action of internal high pressure
and accommodated in the mold of an internal high pressure
forming tool, it being possible for the punch to be
pushed from the mold wall into the mold interior space,
characterized in that the punch (1) is designed so as to
taper at an angle toward the cutting edge (3) in its
region plunging into the part (2) to be punched and forms
a sealing surface.
2. The punch as claimed in claim 1, characterized in
that the punch (1), in its initial position, is arranged
in the mold in such a way that the cutting edge (3) is
set back relative to the mold inner wall.
3. The punch as claimed in claim 1 or 2, characterized
in that the angle of taper is greater than 0° and is at
most 30°.

Description

CA 02549547 2006-06-13
P803396/T~10/1
DaimIerChrysler Ac3
Punch for producing holes in the wall of hollow parts
subjiected,to the action of internal high pressure
The invention relates to the design of punches for
producing holes in the walls of hollow parts, the part
being subjected to the action of high pressure in the
interior by a medium during the punching.
In particular when producing hollow parts by the internal
high pressure forming process, it is normal practice,
following the forming and with the part still located in
the forming tool, to make holes in the wall.
DE 43 22 063 C2 discloses a method and a device for
cutting out a blank from a wall. of a hollow body produced
according to the internal high pressure forming process.
In this case, the blank is cut out directly after the
internal high pressure forming by means of a punch acting
from outside on the lateral surface of the hollow body.
To this end, the driven punch passes through the internal
high pressure forming tool. A tool of the generic type is
described in DE 199 34 663 A1.
when cutting through the hollow body, a pressure drop in
the hollow body inevitably occurs due to the resulting
leakage. If a plurality of holes are to be made in the
hollow body, the holes must be made exactly
simultaneously so that the internal pressure required for
satisfactory punching is available during all the
- punching -operations. This simultaneity of the punch
drives requires considerable control input and very high
pumping capacities ox correspondingly large accumulators..
Also disadvantageous is the extremely abrupt loading of
the hydraulic components.

CA 02549547 2006-06-13
P803396/WO/1
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The object of the invention is to design the punches for
use of the generic type in such a way that a drop in the
internal high pressure when cutting through the wall of
the part is largely avoided.
This object is achieved by a punch design according to
the features of patent claim 1. Detailed configurations
of the punch are specified in the subclaims.
The punch is designed eo as to taper at an angle in the
direction of the cutting edge in ite region plunging into
the part to be punched. As a result, during the cutting,
the material in the region of the hole wall is upset in
accordance with the tapered outer contour of the punch,
and the hole is immediately sealed by the punch. In this
way, when making a plurality of holes, the punches can be
moved slowly and asynchronously to one another with
respect to time. The quality of the holes produced and
the process reliability increase considerably as a
result. The cost in terms of equipment can be kept
correspondingly law, since the tools can be of simpler
and more compact design. Thus no expensive measures are
required for achieving synchronized sequences, such as
tool bridges or electronic path control.
An exemplary embodiment of the invention is shown in the
drawing and described in more detail below.
In the drawing:
fig. 1 shows a diagrammatic illustration of a punch
before the punching,

CA 02549547 2006-06-13
P803396/WO/1
- 3 -
fig. 2 shows a diagrammatic illustration of a punch after
the punching.
Figure 1 shows, in a partial section, a hollow part 2
which is preferably produced by the internal high
pressure forming process and is still subjected to the
action of internal high pressure and which bears with its
outer contour against the inner wall of an internal high
pressure forming tool 4. In the internal high pressure
forming tool 4, a punch 1 is arranged in such a way as to
be movable in the arrow direction preferably by means of
a hydraulic drive (not shown). In its region plunging
into the part 2, the punch 1 is designed to taper
comically toward the cutting edge 3. The angle of taper
is in this case greater than 0° and is at most 30°, but
preferably 1° to 3°. In this case, the cutting edge 3 of
the punch 1 is set back slightly relative to the mold
inner wall of the internal high pressure forming tool 4.
To make the hole, the punch 1 is moved in the direction
of the part 2, and the cutting edge 3 cuts through the
wall of the part in the process. The comically designed
region of the punch I up$ets the material in the region
of the hole wall 5 a.nd the hole is simultaneously sealed
by the punch I. Therefore no drop in the internal high
pressure occurs (fig. 2).
Since the internal high pressure is maintained in this
way, it is possible, without any problems, to make
further holes asynchronously with respect to time using a
plurality of punches._ -

Representative Drawing