Metal deforming – By application of fluent medium – or energy field – With cutting
Reexamination Certificate
2000-08-18
2001-07-17
Jones, David (Department: 3725)
Metal deforming
By application of fluent medium, or energy field
With cutting
C083S698910
Reexamination Certificate
active
06260393
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to so-called high-pressure bulge forming. More particularly this invention concerns punching a hole in a workpiece produced by such high-pressure shaping.
BACKGROUND OF THE INVENTION
As described in commonly owned U.S. Pat. Nos. 5,628,220 and 5,765,420 of Schafer is it known to bulge-form a workpiece, normally a tube, by fitting it to a die and then internally pressurizing the workpiece to such a high pressure that it is deformed outward to take the shape of the tool or die. The result is a very strong cold-formed piece whose shape perfectly corresponds to that of the die.
It is often necessary to punch a hole in such a workpiece. Rather than do this as a separate step from outside, it is known from German 195 06 067 of Herberg and from U.S. Pat. No. 5,460,026 of Schafer to provide the shaping tool with a punch assembly comprising a guide sleeve whose inner surface is flush with an inner surface of the tool cavity and a punch fitting complementarily in the guide sleeve and movable between an inner position projecting into the tool slightly past the sleeve and an outer position recessed back in the sleeve.
During the initial shaping operation the punch is advanced slightly to its inner position to produce an inwardly raised region of the same shape of the punch and having an outer periphery defined by a line of reduced thickness where the material of the workpiece is stretched over the edge of the punch. The punch is then retracted and, if necessary, the pressure in the workpiece is increased to drive out the piece and cut it off at the weakened line. This procedure is extremely convenient in that it is done right in the shaping tool during the initial formation operation, and the cut-out piece ends up outside the workpiece.
The disadvantage of this system is that the subassembly formed by the punch and its guide sleeve must be meticulously mounted in the tool and secured very solidly in place. This is typically done by bolting a holding plate over the outside of these parts. Thus when they need to be changed, it is necessary to remove a relatively bulky holding plate and then pull out the sleeve and punch.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved punch for a high-pressure shaping tool.
Another object is the provision of such an improved punch which overcomes the above-given disadvantages, that is whose punch subassembly can be easily removed and replaced.
SUMMARY OF THE INVENTION
A punch assembly for a high-pressure shaping tool having a seat opening into the tool has according to the invention a guide sleeve fitted in the seat, centered on an axis, and having a radially outwardly directed outer surface radially confronting an inner surface of the seat. A punch is axially displaceable in the sleeve. A clamping element engaged radially between the inner seat surface and the outer sleeve surface retains the sleeve in the seat.
This system solidly holds the sleeve in place, but does not require that bulky holding plate and such be mounted over the outer end of the sleeve. Thus the tool is not made substantially more massive in the region of the punch assembly.
The seat is formed with a radially inwardly open groove and the element is a ring engaged in the seat. A screw can serve for pressing the ring radially against the punch. Alternately the ring is pressed radially against the punch by fluid pressure applied radially outside the ring. The ring is elastomeric and is normally of C-section.
The element according to the invention can be at least one ball seated in the sleeve. The seat is formed with a radially inwardly open recess in which the ball is engageable. More particularly the sleeve is formed with a radially throughgoing bore receiving the ball and has a radial thickness at the bore that is smaller than a diameter of the ball so that when the punch is inserted in the sleeve it pushes out the ball so it projects radially from the sleeve. The punch has a chamfered inner end engageable with the ball.
Furthermore in accordance with the invention the tool includes an outer sleeve coaxially surrounding the inner guide sleeve. The assembly further has a clamping element engaged radially between the inner seat surface and an outer surface of the outer sleeve. This clamping element can be a ring like that usable on the inner sleeve.
REFERENCES:
patent: 3114280 (1963-12-01), Schott
patent: 3600999 (1971-08-01), Daniels
patent: 3715947 (1973-02-01), Weisbeck et al.
patent: 5398533 (1995-03-01), Shimanovski et al.
patent: 5460026 (1995-10-01), Schafer
patent: 5628220 (1997-05-01), Schafer
patent: 5666840 (1997-09-01), Shah et al.
patent: 5765420 (1998-06-01), Schaefer
patent: 5996455 (1999-12-01), Haag et al.
patent: 6098437 (2000-08-01), Kocer et al.
patent: 6158122 (2000-12-01), Skudutis
patent: 195 06 067 (1996-03-01), None
Engel Bernd
Lackner Martin
Dubno Herbert
Jones David
Schuler Hydroforming GmbH & Co. KG
Wilford Andrew
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