TOOL HOLDER WITH PUNCHING UNITS

PORTE-OUTILS COMPORTANT DES UNITES A POINCON

English Abstract

A tool holder for a punching machine, comprising several punching units (14)
that are accommodated in tool holding fixtures (12) in the holder (10) in
addition to gas pressure springs (15) to recall the punches (20). The
advantage of gas pressure springs is that the pressure level can be adapted to
the material that is to be machined. In order to make it easier and quicker to
achieve said adaptation, the pressure chambers (28, 32) of the gas pressure
springs are joined to a common supply line (44) which can be connected to a
pressure gas source. As a result, it is possible to change the internal
pressure of all the gas pressure springs (15) at the same time.

French Abstract

L'invention concerne un porte-outils destiné à une presse à découper, qui comporte plusieurs unités à poinçon (14) qui sont logées dans des logements d'outil (12) du support (10) et présentent des ressorts à pression de gaz (15) pour le rappel des poinçons (20). L'avantage offert par les ressorts à pression de gaz réside dans la possibilité d'adaptation du niveau de pression à un matériau à travailler. Pour obtenir, avec des supports multiples, une adaptation plus rapide et plus simple, il est proposé que les chambres de pression (28, 32) des ressorts à pression de gaz (15) soient raccordées à une conduite d'alimentation (44) commune pouvant être reliée à une source de gaz sous pression. On obtient ainsi la possibilité de modifier simultanément la pression intérieure de tous les ressorts à pression de gaz (15).

Claims

Claims
1. A tool holder for a punch press with several punching
units (14), which are seated in tool receivers (12) in the holder
(10) and have gas pressure springs (15) for retracting the
punches, characterized in that the pressure chambers (28, 32) of
the gas pressure springs (15) are connected to a common feed line
(44), which can be connected to a compressed gas source.
2. The tool holder in accordance with claim 1,
characterized in that the feed line (44) constitutes a pressure
reservoir.
3. The tool holder in accordance with claim 1 or 2,
characterized in that a control valve for setting a defined
pressure level in the feed line (44) is provided between the
compressed gas source and the feed line (44).
4. The tool holder in accordance with one of claims 1 to
3, characterized in that control valves for setting a defined
pressure level in the respective pressure chambers (28, 32) are
provided between the feed line (44) and at least a portion of the
pressure chambers (28, 32).
5. The tool holder in accordance with one of the preceding
claims, characterized in that it is designed in a revolver shape
and the punching units (14) are circularly arranged.
6. The tool holder in accordance with claim 5,
characterized in that the feed line (44) is annularly arranged
between the punching units (14).
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7. The tool holder in accordance with one of the preceding
claims, characterized in that the compressed gas is nitrogen.
-6-

Description

CA 02336066 2000-12-22
Tool Holder with Punching Units
The invention relates to a tool holder for a punch press
with several punching units, which are seated in tool receivers in
the holder and have gas pressure springs for retracting the
punches.
Besides the widely used steel springs embodied as helical
or plate springs, punching units with gas pressure springs are
known, for example from EP 0 646 427. The advantage of gas
pressure springs lies in the possibility of actively affecting the
characteristic spring curves by changing the pressure level in the
pressure chamber of the gas pressure spring. It is possible in
this way to match the spring force to the material to be worked so
that, for example when working thick sheet steel plates, a very
high pressure is generated in the pressure chamber, and when
working thin aluminum sheets a comparatively low pressure is
generated in the pressure chamber. The low pressure when working
soft materials prevents damage to the delicate, possibly already
coated surfaces.
This capability of setting is provided in known punching
units with gas pressure springs, but in connection with tool
holders, however, which can easily have ten or more tool receivers
for punching units, it has been shown to be very complicated to
match the pressure level in all pressures chambers of the
individual punching units to the material to be worked.
It is the object of the invention to create a tool holder,
whose punching units, which are provided with gas pressure
springs, can be matched in a faster and simpler manner to the
material to be worked.
This object i.s attained in accordance with the invention in
that the pressure chambers of the gas pressure springs of a tool
holder of the type described at the outset are connected to a
common feed line, which can be connected to a compressed gas
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CA 02336066 2000-12-22
source.
Because of the central pressure supply for all pressure
chambers, there is the possibility to change the interior pressure
of all gas springs simultaneously. The resetting times in
connection with changing the materials to be worked are thereby
considerably reduced. The common pressure supply also assures an
even pressure level in all gas pressure springs, should this be
desired.
The feed line preferably constitutes a pressure reservoir.
The relatively large volume of the feed line leads to mare
flattened characteristic curves of the gas pressure springs, since
the displaced volume of one gas pressure spring in the course of a
punch stroke is relatively small in relation to the entire
pressure volume. In contrast thereto, a gas pressure volume of
comparable size can hardly be realized in the area of the gas
pressure springs, since the structural space is greatly limited by
the conditions of the tool holder and the punch press.
In a preferred embodiment of the invention, a control valve
for setting a defined pressure level in the feed line is provided
between the compressed gas source and the feed line. The control
valve makes possible the exact setting of the pressure level if a
pressure supply container of a given, very high pressure is used
as the compressed gas source.
In a further embodiment of the invention it is provided
that control valves for setting a defined pressure level in the
respective pressure chambers are provided between the feed line
and at least a portion of the pressure chambers. Such an
arrangement makes possible the individual setting of the pressure
level in the various pressure chambers, in order to match the
several punching units individually to the conditions. Depending
on the effective piston surface and the type of the punch, an even
more exact optimization of the restoring forces to the respective
worked material is possible with this.
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CA 02336066 2000-12-22
In a typical embodiment, the tool holder is designed in a
revolver shape, and the punching units are arranged in a circle.
With this type of tool holders the feed line is preferably
arranged in a ring shape between the punching units. This
arrangement is particularly advantageous because there is
sufficient space available for the feed line in the space between
the punching units, so that refitting of existing tool holders,
which up to now had been used with punching units with steel
springs, is easily possible.
Nitrogen, which is not inflammable, not poisonous and
inexpensive, is preferably used as the compressed gas.
Exemplary embodiments of the invention will be covered in
greater detail by making reference to the attached drawings.
Shown are in:
Fig. 1, a schematic top plan view of a tool holder with a
feed line for gas pressure springs in the punching units,
Fig. 2, a cross section through the tool holder in Fig. 1.
A tool holder 10, which can be inserted into a turret punch
press, is represented in Fig. 1. The tool holder 10, which is
designed disk-shaped, has receivers 12 (see Fig. 2), which are
arranged in the shape of a circle and in which punching units 14
are received. In the exemplary embodiment represented, the
structure of the punching units 14 follows that described in DE
195 05 754, however, the plate spring packages provided there are
replaced by gas pressure springs, such as are basically known from
EP 0 708 267.
Otherwise, the punching units 14 consist of a guide bushing
16, a multiple punch driver 18 and a punch 20, connected with the
punch driver 18 by means of a screw 19. A stripper plate 22 is
provided between the lower end of the guide bushing and the punch
20. The gas pressure spring is arranged between a radially
projecting head 24 and the rear end wall of the guide bushing 16.
The gas pressure spring 15 has a housing 26, which is
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CA 02336066 2000-12-22
essentially circular in cross section and in which cylindrical
bores 28 are arranged, in each of which a piston 30 is guided in
an axially displaceable manner. The cylindrical bores 28 are
connected with each other via an annular conduit 32 and together
constitute the pressure chamber of the gas pressure spring 15.
The pistons 30 are sealed in respect to the walls of the
cylindrical bores 28 with the aid of seal rings 34. The annular
conduit 32 has a connecting conduit 36, into whose opening 38 a
feed hose 40 is screwed by means of an appropriate threaded
element. All punching units 14 in the exemplary embodiment
represented have an identical structure, however, it would also be
conceivable to combine punching units of different structure and
differently designed gas pressure springs.
The feed hoses 40 of all punching units 14 are connected by
means of suitable connectors 42 to an annular feed line 44, which
is arranged centered in the center of the tool holder 10. The
feed line 44 itself has a pressure connector 46, which is
connected with a compressed gas source (not represented). A
control valve is arranged between the pressure connector 46 and
the compressed gas source, by means of which the pressure level in
the feed line 44 can be accurately set.
With the embodiment shown, wherein all pressure chambers
are in constant connection with the feed line 44, the same
pressure level as in the feed line 44 is present in all pressure
chambers. It is also possible to provide additional control
valves between the feed line and the individual pressure chambers,
with whose aid the individual pressure levels in the separate
chambers can be affected.
With other shapes of tool holders, the feed line would be
matched to the structural space available in accordance with the
shape of the tool holder and the arrangement of the punching
units.
MPlO.DOC -4-

Representative Drawing