Metal deforming – By application of fluent medium – or energy field – Using fixed die
Reexamination Certificate
2001-07-05
2003-06-10
Jones, David (Department: 3725)
Metal deforming
By application of fluent medium, or energy field
Using fixed die
C072S058000, C029S421100, C029S254000
Reexamination Certificate
active
06575007
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a device for forming a hollow profile formed as a single or multi-chamber profile by means of an internal high pressure generated by a fluid pressure medium within the hollow profile, containing a sealing die engaging in the profile chamber with a carrier part and, arranged directly or indirectly on the carrier part and sealing the face of a profile chamber, a collar with a base part and containing at least one passage opening as a pressure medium supply and/or extraction channel, and a process for internal high pressure forming.
In internal high pressure forming, referred to below as the IHU process, a hollow profile is expanded by internal pressure. For this the faces of the hollow profile are sealed in order to build up and maintain an excess pressure in the interior by means of a pressure medium. The excess pressure leads to an expansion of the hollow profile. The hollow profile assumes the form preset by the tool mold in which the hollow profile was previously laid. Former sealing processes use conical metal sealing dies in particular steel dies, which are introduced into the hollow profile. In addition, the hollow profile can be pushed further by means of at least one die part acting on the face of the workpiece. In this way it is possible to expand or swage the workpiece.
In a double or multi-chamber profile, the webs between the individual chambers stretch during forming differently from the other walls or outer contours, and the die is unable to compensate for the uneven distortion. If the tolerances of the profile cross-section are selected to be too large, e.g. more than 0.1 mm, sealing in the conventional manner is not possible. This had led to attempts to use sealing dies of plastic, in particular polyurethane.
However, conventional sealing dies with polyurethane collars wear quickly due to the friction occurring on introduction into the hollow profile and excessive compressive stresses at sharp corners and step-like changes in wall thickness of the collar. If the form of the profile deviates too greatly from the nominal values, the sealing element must be introduced even further which increases the wear. Also, the required sealing effect can no longer be achieved.
SUMMARY OF THE INVENTION
In view of these circumstances it is an object of the present invention to provide a reliable and comparatively simple sealing system suitable for series production, in particular for multi-chamber profiles, which ensures optimum sealing capacity in the mating between the hollow profile, in particular the multi-chamber hollow profile, and the die, and improved die tool lives. The increase in tool life in standard operation should lead to a reduction in operating costs.
The task according to the invention is solved in that the collar is a resilient rubber die part arranged on the face of the carrier part facing the profile chamber and the base part is designed block-like and the outer wall of the base part is formed conical completely or at least in its end section facing the profile chamber and tapering towards the profile chamber, and the stop point of the profile chamber face which is effective for sealing for forming lies on the conical section of the outer wall of the base part.
The die according to the invention is aligned with the longitudinal die axis x which corresponds suitably to the direction of insertion of the die. The collar preferably comprises or contains a plastic with limited resilience. The collar in particular comprises or contains in particular polyurethane. The base part of the collar is characterised by a solid compact block-like structure. The base part has for example a diameter to height ratio of 0.5 to 6, in particular from 1.5 to 5.
In the preferred embodiment, on the free face of the base part is arranged a preload plate anchored by way of fixing means in the carrier part lying directly or indirectly on the collar, and preloading the collar and mounted to be twist-resistant.
The preload plate is a flat plate-like element and suitably consists of a high strength material so that it can exert a contact pressure on the collar in the preloaded state without itself being substantially deformed. The preload plate preferably consists of a ferrous or non-ferrous metal, in particular steel. The preload plate suitably has a through-bore preferably arranged centrally, which advantageously serves as a passage opening for the pressure medium supply and/or extraction. The area of the preload plate is preferably more than 60%, in particular more than 75%, of the average cross-sectional area of the collar.
The collar lies with a base surface on the carrier part. On the side opposite the base surface the collar contains a free face. The collar also has a passage opening, preferably arranged centrally, aligned with the passage opening of the preload plate and which constitutes the continuation of the pressure medium supply and/or extraction channel.
The peripheral geometry of the collar is suitably adapted to the inner contour of the profile chamber of the chamber profile. The base part of the collar suitably has an outer wall around its full periphery. The outer wall of the base part can run completely or in sections parallel to the die longitudinal axis x or taper in the direction of the free face i.e. in the insertion direction of the die.
In the latter case the acute angle enclosed by the outer wall and the die longitudinal axis x is preferably less than 20°, in particular less than 10° (angle degrees) and preferably greater than 0°, in particular greater than 3°. The outer wall of the base part preferably contains the stop point of the profile chamber face effective for sealing for profile forming.
In a preferred embodiment of the invention, the outer wall of the base part is formed conically completely or at least in its end section facing the profile chamber and tapering towards the profile chamber, and the stop part of the profile chamber face effective for sealing is provided on the conical section of the outer wall of the base part for profile forming.
The outer wall can also have a more strongly tapering end section wall in the transition to the face in the insertion direction of the die. The surfaces of the outer wall and the end section wall preferably enclose an acute angle of 0° to 45° (angle degrees), in particular 10° to 30°. The greater taper of the end section wall facilitates insertion of the die into the profile chamber.
In a first embodiment of the invention the collar has a pocket-like recess arranged on the face against the profile chamber which is surrounded by a ring flange preferably on the full periphery. The pocket-like recess contains a face which is set back. In this embodiment the collar consists of a base part with outer wall and a ring flange arranged on the base part and forming the pocket-like recess, with a ring flange outer wall and a ring flange inner wall directed towards the pocket-like recess. The ring flange outer wall preferably sits at the level of the ring flange shoulder and constitutes an end section wall described above.
The ring flange can also lead merely over part sections of the total periphery of the collar, and in particular cover only the corner areas of the adjacent external walls of the collar. The cross-sectional diameters of the ring flange remain, preferably, where applicable with the exception of the corner areas, constant over the entire periphery of the collar such that the pocket-like recess and with it the preload plate substantially reproduce the cross-sectional geometry of the profile chamber.
The ring flange and base part, i.e. the collar, are suitably made of one piece. The ring flange is suitably formed bead-like. The height of the ring flange preferably corresponds to the thickness of the preload plate and in particular deviates from the thickness of the preload plate by no more than ±50%.
Between the ring flange inner wall and the face of the base part is formed a transition area. In the preferred design a curved surface, in parti
Göger Aslan
Hein Jörg
Rost André
Alcan Technology & Management Ltd.
Jones David
Ostrolenk Faber Gerb & Soffen, LLP
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