Electric heating – Inductive heating – Metal working
Reexamination Certificate
2001-02-20
2003-10-07
Van, Quang T. (Department: 3742)
Electric heating
Inductive heating
Metal working
C219S617000
Reexamination Certificate
active
06630649
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to methods and apparatus for inducing physical changes in metal objects in general and making use of pulsed magnetic force (PMF) energy therefor, in particular.
BACKGROUND OF THE INVENTION
The employment of PMF, for forming, joining or welding of metal objects is known in the art. In this process, current is rapidly discharged through a coil, which is proximal to the workpiece. Owing to eddy currents in the workpiece, an intense magnetic pressure builds up, which may perform work on at least a portion of the workpiece. Typically, the portion of the workpiece, which is proximal to the working coil of the PMF apparatus, is induced into a rapid movement and the kinetic energy associated with this movement gives rise to said physical change. The change may be forming namely a change in the shape of the object. At times, the rapid movement of said portion is induced only on a microscopic scale. For example, in the case of joining or welding two metal workpieces, portions thereof are placed into close proximity and they in fact touch one another. But nevertheless notwithstanding this close proximity some clearance between the two remains even if only on a microscopic scale which permits a short rapid movement of a portion of at least one of the workpieces (obviously over only a very short distance). This suffices for the build-up of kinetic energy, which dissipates upon impact with a portion of the other workpiece and may give rise to joining or welding of the two workpieces to one another.
GENERAL DESCRIPTION OF THE INVENTION
The present invention is directed to a method and apparatus for working, i.e. inducing physical change in at least one metal workpiece. The term “physical change” denotes structural change in form or shape, cutting off of a portion of a workpiece, perforation of a workpiece, joining of two or more workpieces to one another or welding two workpieces or portions thereof to one another. The term “joining” used before and further below means to denote a tight engagement of two workpieces to one another, for example, tight fitting of a generally cylindrical object over a tubular object fitted within it; and the term “welding”, in distinction from joining, means to denote a very tight interaction of the surfaces of two objects, e.g. metalurgical bonding of at least a portion of the two workpieces.
The method and apparatus of the invention make use of pulsed magnetic force (PMF) energy. In accordance with the invention, PMF energy is combined with another energy from a separate energy source which acts synergistically with the PMF energy to impart a physical change. The other energy source (to be referred to herein at times as the “auxiliary energy source”) may be another PMF energy, may be a mechanical energy source, and many others.
In accordance with a first aspect of the invention there is thus provided a method for inducing a physical change in at least one metal workpiece, comprising:
(a) transferring at least one pulse magnetic force (PMF) energy to at least a portion of the at least one workpiece for inducing an intense magnetic pressure therein; and
(b) transferring an auxiliary energy at least partially co-extensive with the PMF energy to the at least a portion of the workpiece whereupon the PMF and auxiliary energies combine to yield the physical change.
In accordance with another aspect of the invention there is provided an apparatus for inducing a physical change in at least one metal workpiece, comprising:
(i) at least one PMF unit with a forming coil for the discharge of current therethrough to induce an intense magnetic pressure in at least a portion of the metal workpiece; and
(ii) at least one auxiliary energy source for transferring, at least partially co-extensive with the current discharge through the forming coil, an auxiliary energy to the at least a portion of the workpiece such that said pressure and auxiliary energy synergize to yield said physical change.
The term “transferring energy” or any similar term which may be used herein, means to denote the transfer of energy to a workpiece in a form which at least partially acts to yield said physical change. The term “metal workpiece” refers to any metal object which is to be worked by the method or apparatus of the invention, which may be a cylindrical object which is to be joined or welded to a tubular or another cylindrical objection; a metal plate which is to be formed, cut or perforated; etc. As will be appreciated, the invention is not limited to a workpiece of any specific kind but rather can be applied for a myriad of different workpieces and for inducing a wide variety of different physical changes.
The term “combination of energies” or the like means to denote the timed activation of the at least two energy sources to transfer their respective energies to the at least one workpiece such that the periods of their transfer at least partially overlap, whereby the combined effect of the two energies, as far as inducing the physical change, is substantially larger than the physical change which may be imparted by only one of the energy sources. The combination of energies in accordance with the invention gives rise to a variety of improvements over the use of PMF alone. For example, in the case of welding or joining of two metal workpieces to one another, the same result may be achieved with a lower PMF energy as compared to PMF alone. This may have design consequences as the generation of a large PMF necessitates large capacitor banks and thus an apparatus in accordance with the invention may have an overall smaller size.
Additionally, the present invention allows the achievements of results, which may be difficult to achieve in accordance with the prior art. For example, in the case of welding two tubular workpieces to one another, with one enveloping the other, the strong impact of the external one onto the internal one, may give rise to squeezing or crushing of the internal tubular workpiece. However, in accordance with the invention, which permits use of smaller PMF pulses for achieving the same effect, such an undesired effect may be eliminated or reduced. In the case of welding, the combination of energies in accordance with the invention may give rise to an increase of the area of the weld.
At least for the case of welding, it is preferred that the time period overlap be substantial, meaning that at least one of the energies is applied such that throughout most of its period of application, it overlaps the other applied energy. This may mean, for example, that both may begin and end simultaneously, both may begin simultaneously and end in succession, both may begin in succession but end simultaneously, one beginning and ending during the period the other energy is applied, and various combinations of these scenarios.
While one energy source is always a PMF energy source from a PMF device, to be referred to herein at times as “primary PMF energy source”/“primary PMF device”, the other energy source may be selected from a wide variety of different sources. In accordance with one preferred embodiment, the other energy source is an auxiliary PMF energy source of a different specification. In accordance with other embodiments, the other energy source is a device for generating a mechanical shock wave or mechanical vibrations in the workpiece; a device which can generate ultrasonic vibrations within the object, e.g. a device as customary used in ultrasonic welding; a device for transferring an electric current through an interface between portions of workpieces which are to be welded to one another, such as that used in resistant welding; etc.
It should be noted that the term “primary” used above and further below, does not mean to denote that this energy source is of prime importance as compared to other sources of energy used in accordance with the invention. Similarly, the term “auxiliary” should not be understood as meaning secondary in importance. Rather, these terms are used merely for the sake of convenience. It should be appreciated th
Gafri Oren
Livshiz Yuri
Browdy & Neimark, P.L.L.C.
Van Quang T.
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