Metal deforming – By extruding through orifice – Container and/or support therefor
Patent
1994-08-26
1995-10-31
Larson, Lowell A.
Metal deforming
By extruding through orifice
Container and/or support therefor
722531, B21C 2704
Patent
active
054618991
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a sealing device for an extruder for the evacuation of air, the extruder including a cylinder with a die and a reciprocating piston.
In the production of longitudinal metal sections by the traditional method, a shaping machine of the above type is used. A metal billet with a circular cross-section is preheated and placed in the cylinder. Then the piston presses the billet through the die with great force. The extrusions thus formed take on different shapes depending on the shape of the hole in the die.
Work is being done to develop methods of producing metal sections based on the use of particulate material such as metal powder or needles. However, when one uses particulate material to make a bolt or metal extrusion, there are increased problems with air pockets and moisture, and this detracts form the quality of the extrusion.
EP Patent Application No. 0397423 describes a method and equipment for producing metal objects by consolidation of particulate material, using an extruder with a solution for the evacuation of gas. A piston is used with a wedge, where the gas is sucked out past the wedge and through a bore in the piston. This solution gives an end product which is very close to optimum, i.e. which to all intents and purposes is without deleterious impurities and pores, and which has an almost impermeable surface which prevents absorption of humidity and gas during later use. However, there is one disadvantage with such equipment, i.e. that it does not achieve a satisfactory seal between the piston and the cylinder, and this in turn means that air is drawn into the cylinder during the extraction operation when a strong vacuum is used.
Also known is an extruder where air is extracted from the extruder cylinder by means of a venting plate which is pressed against a venting ring mounted on the cylinder. The venting plate can be moved by means of piston/cylinder mechanisms. This solution is complicated and costly. In addition, it requires a great deal of space and would obstruct the movements of anyone operating it.
SUMMARY OF THE INVENTION
The present invention provides a sealing device for an extruder which provides an almost complete seal, and which, combined with the use of an efficient vacuum pump, can provide pressures lower than 10.sup.-3 atm. The pressure can be further reduced by using a molecular or diffusion pump.
With this invention there is provided a sealing mechanism for an extruder wherein a separate sealing mechanism is installed at the inlet, which sealing mechanism accompanies the piston when it is retracted from the cylinder.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described in more detail by means of an example and with reference to the attached drawing, wherein:
The single FIGURE is a partial cross-section of an extruder according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The extruder of the invention includes a cylinder 1, a piston 2, and a sealing device 11. A die of the extruder, equipment for feeding particulate material and a hydraulic arrangement for moving the piston are not shown in the drawing and will not be discussed in more detail. The cylinder 1 is provided with a generally radial hole or bore 6 that extends axially inclined from another end thereof to an inner end thereof opening into the cylinder 1. The bore 6 is furnished with a threaded steel pipe (not shown) which in turn is connected with a vacuum pump (not shown).
To obtain a seal between the cylinder and a piston rod 3, sealing device 11 is installed outwardly of the piston rod 3 and the piston 2. Device 11 includes a casing 4, mainly of aluminum, furnished with an inside seal 8 sealing against the piston rod 3 and a V-shaped ring 9 of heat-resistant material sealing against an end of the cylinder 1. On the front of casing 4 a series of permanent magnets 7 is attached against the cylinder 1. The permanent magnets keep the casing 4 centered, i.e. in position in relation to the cylinder 1 until a vacuum arises i
REFERENCES:
patent: 2107896 (1938-02-01), MacKnight
patent: 3369384 (1968-02-01), Beneke et al.
patent: 3705509 (1972-12-01), Haller
patent: 3779063 (1973-12-01), Gannon
patent: 3835685 (1974-09-01), Kent et al.
patent: 4714423 (1987-12-01), Hattori et al.
Auran Lars
Sorheim Ole Johan
Vik Kai Magne
Larson Lowell A.
Norsk Hydro a.s.
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