Metal deforming – By use of closed-die and coacting work-forcer – Forcing work into or within closed die; e.g. – forging
Reexamination Certificate
2002-02-06
2004-03-02
Crane, Daniel C. (Department: 3725)
Metal deforming
By use of closed-die and coacting work-forcer
Forcing work into or within closed die; e.g., forging
C072S355400, C072S407000
Reexamination Certificate
active
06698267
ABSTRACT:
TECHNICAL FIELD
The invention relates to a method of forming a body of a formable working material in an impact machine, which comprises an upper impact unit with an upper ram, an upper punch, a lower impact unit with a lower ram, a lower punch, and a mould cavity for the working material between the punches when the punches are brought towards one another. The invention also relates to an impact machine for the carrying out of the method.
BACKGROUND ART
Impact machines for working by the employment of high kinetic energy are machines for working in the first place metal, such as cutting, punching, and plastic forming of powder-components, powder compaction, and similar operations, in which the speed of a ram, which may consist of a press piston, may be essentially higher than in conventional presses. Also polymeric and ceramic working materials can be conceived, as well as various composites of metals, polymers and ceramic materials. The working principle is based on the development of a very high kinetic energy of short duration instead of a high static press force of long duration. The dynamic forces of short duration which are generated at the ram impact and which in impact machines of prior art are conveyed around in the system via stand and foundation may be several thousand times larger than in conventional presses and imply that considerable amounts of energy are lost in stands and foundations instead of being used for effective work at an optimal way. In order to be able to absorb large force pulses, impact machines of prior art are equipped with very strong and heavy stands and foundations according to principles which are common in connection with conventional presses. Nevertheless the dynamic, shock type force pulses that are developed in impact machines are not damped in such heavy, conventional systems. The stress on all joints therefore become very large, as well as on sensitive components, e.g. electronic components for controlling those hydraulic valves which usually form parts of impact machines, which may cause a great risk of failure. Large, unwieldy stands also give rise to problems in connection with service, change of tool unit or of tool insets in the tool unit, changing the height of the impact unit above the tool unit, etc.
BRIEF DISCLOSURE OF THE INVENTION
It is the purpose of the invention to address the above complex of problems. More particularly, the invention aims at achieving in the first place the following advantages:
to provide that the kinetic energy of rams can be used essentially for effective work in connection with the working of a working material instead of being lost in tools and auxiliary equipment, such as stand and foundation, which in turn can create improved possibilities to work and/or to form materials which previously have not been possible to be worked and/or formed to a desired degree,
to counteract shock waves from the impact via the machine stand, which in turn makes it possible to use a substantially lighter stand, and to eliminate heavy bases, which according to prior art have had the purpose of absorbing shock waves,
to reduce the total mass of the machine in comparison with known comparable impact machines, including reducing the sizes of the impact units, at the same time as lower striking velocities can be employed for the achievement of desired working, and
to make it possible to compact metal powders or other formable powder, such as ceramic powders or composite powders consisting mainly of metal, ceramic and/or polymeric powders, to a higher and more even density than what has been possible by means of prior art because of losses of energy in tools and auxiliary equipment.
The characteristic feature of the invention is that a body is formed of a formable working material in an impact machine comprising an upper impact unit with an upper ram, an upper punch, a lower impact unit with a lower ram, a lower punch, and a mould cavity for the working material, wherein downwards movable masses, which comprise at least the mass of the upper ram and the mass of the upper punch, and upwards movable masses, which comprise at least the mass of the lower ram and the mass of the lower punch, are caused to be moved towards one another and towards the working material in the mould cavity; that the masses which move downwards, including the upper punch, obtain a downwards directed velocity v
1
, and the masses which move upwards, including the lower punch, obtain an upwards directed velocity V
2
, wherein the movable parts have such masses and the velocities are so high that the momentum of the downwards movable masses and the upwards movable masses become essentially equal, i.e. such that the following condition applies:
m
1
×v
1
≅m
2
×v
2
where m
1
is the total mass of the masses moving downwards, and m
2
is the total mass of the masses moving upwards plus the impact;
that the kinetic energies of the movable masses, i.e.
m
1
v
1
2
2
,
and
m
2
v
2
2
2
,
respectively, are essentially transferred to the working material in the mould cavity and are so great that the working material is plasticized and flows out to fill all parts of the mould cavity, when the punches are maximally brought together, for the formation of said body with desired shape.
According to a preferred method of carrying out the method, the body is formed of the formable working material in an impact machine which also comprises a central unit, said central unit including a die having a through hole which together with the upper punch and the lower punch form said mould cavity, said die being essentially stationary during the impact operation.
However, one can also conceive, according to an alternative embodiment, particularly for forming comparatively thin objects, that the machine has no central unit with a die, wherein the mould cavity is formed between the punches without any surrounding die, i.e. therein that one or both punches, preferably at least the lower one, is engraved, i.e. is embossed.
Prior to the impact, the upper punch and the lower punch preferably are pressed from above and from below, respectively, by a downwards directed force and by an upwards directed force, respectively, causing a static pressure from above and from below, respectively.
What is particularly characteristic according to an aspect of the invention, is that the upper and lower impact units can be raised and lowered in a controlled way for the setting of predetermined lengths of the upper ram and of the lower ram, respectively, prior to the forming operation in the case that the machine comprises an essentially stationary, central unit, wherein, according to this aspect of the invention, the upper and lower impact unit may be vertically adjustable in a controlled way relative to said central, essentially stationary unit.
Because of the short duration of the pressure pulse, when the material in the mould cavity is worked in a symmetrical way due to combined action by momentums from two directions, the risk that the high pressure will deform the punches and/or the die tool is reduced when the machine comprises a die, because of the inertia of the mass of the tool material. This allows for higher pressure in the mould cavity than what is possible according to prior art including forming by employing high kinetic energy, wherein the possibility to plasticize the working material in the mould cavity is improved. Because of the rapid material working, at least according to a conceived embodiment of the method and of the machine, and because of very short movements of the punches, also considerably less friction between the tool and working material will arise, and, in the case that the working material consists of powder, also less friction between the powder grains, which makes a considerably improved yield in the forming and the consolidation process possible, in other words that more energy can be brought to act on the working material. In an uncontrolled process there is a great risk that the tool will be damaged because of large fr
Bednarek Michael D.
Crane Daniel C.
Morphic Technologies Aktiebolag
Shaw Pittman LLP
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