Shock Forming

Abstract

Method of and apparatus for the shock-wave forming of metallic and other workpieces in which an electrical discharge in a liquid produces a shock wave, preferably in a power jet directed against the workpiece. The discharge is produced between a pair of permanent electrodes with a gap between them temporarily bridged at least in part by a fusible conductor. The electrical supply preferably includes at least one high-voltage, low-current source for initiating the discharge and at least one high-current, low-voltage source for sustaining the discharge thereafter. Control of the power jet is effected by fluidic methods using transverse jets of the same or another fluid, preferably under the control of a programmer.

Parent Case Text

The present application is a continuation-in-part of my application Ser. No. 735,760 filed June 10, 1968 (now U.S. Pat. No. 3,566,647) as a continuation-in-part of my application Ser. No. 574,056 filed Aug. 22, 1966 (now abandoned but replaced by application Ser. No. 64,104) as a continuation-in-part of application Ser. No. 311,061 of Sept. 24, 1963, since issued as U.S. Pat. No. 3,276,558 and application Ser. No. 508,487 filed Nov. 18, 1965; of my aforementioned application Ser. No. 508,487 (now U.S. Pat. No. 3,512,384) filed Nov. 18, 1965 as continuation-in-part of application Ser. No. 41,080 of July 6, 1960, since issued as U.S. Pat. No. 3,232,085; of my aforementioned application Ser. No. 574,056 filed Aug. 22, 1966; and of my copending application Ser. No. 696,757 (now U.S. Pat. No. 3,552,653) filed Jan. 10, 1968 as a continuation-in-part of application Ser. No. 574,056 of Aug. 22, 1966 and Ser. No. 629,633 filed Apr. 10, 1967 now U.S. Pat. No. 3,461,268.

Description

This invention relates to shock-wave forming, using electrical discharge energy.

CROSS-REFERENCE TO EARLIER APPLICATIONS

In my earlier application Ser. No. 508,487 filed Nov. 18, 1965, I have described an improved electrode assembly for a discharge-shaping apparatus which imparts relatively long life to the electrodes and which affords maximum utilization of the discharge current. Basically, the apparatus described in that application comprises a generally closed container having at least one flexible wall closely juxtaposed and preferably in contact with the workpiece and filled with a liquid shock-wave-transmitting medium in which an electric discharge is effected.

The vessel may have at least one wall defined by an elastomeric membrane juxtaposed with and advantageously in surface contact with the workpiece along a side of the latter opposite a die whose die cavity is spanned by the workpiece. The discharge generated by the electrodes in this vessel is fattened or augmented to develop a greater discharge pressure by providing an interelectrode spacing somewhat larger than is normally suitable for the generation of a spark discharge and an electrically conductive body is disposed by the electrodes.

In this case, the discharge apparently is subdivided into a pair of somewhat smaller discharges jumping between the intermediate body and the adjacent electrodes at least during the initial portion of the discharge when an ionization of the normally dielectric material in the electrode gaps occurs. Thereafter, the conductivity of the gap increases rapidly and the discharge appears to bridge the two electrodes directly in spite of the fact that a conductive member is disposed between them. A single intermediate member can be disposed centrally between the two electrodes, according to the system described in application Ser. No. 508,487, or else a plurality of equispaced members can be disposed in the gap as required. The use of such intermediate electrodes has been found to sharply increase the discharge pressure available with similar electrical energy utilization.

In the later application Ser. No. 574,056, I have applied the principles of high-energy discharge in the propulsion of particulate materials and the like to coat a substrate, to provide a desired workpiece configuration or otherwise modify the workpiece as a result of the shock wave.

Basically, that system resides in a method of coating metallic substrate by juxtaposing a source of a detonation-type impulsive wave with a surface of the body to be coated and disposed between the body and the source, a mass of a pulverulent materials, preferably in proximity to the detonation source. The production of the detonation-type wave by the source drives the particles onto the substrate with a velocity sufficient to enable them to lodge on the substrate with a firm bond between the coating layer and the substrate.

In accordance with this process, a layer of powder is supported upon a frangible foil, film, sleeve or sheet juxtaposed with the surface to be coated whereby the resulting rupturable diaphragm can separate the discharge chamber from the workpiece chamber. The latter is vented to the atmosphere to prevent the development of pressures resisting high-energy-rate or "kinetic" movement of the particles into bonding engagement with the workpiece and the venting means preferably includes a further damping muffler. The frangible diaphragm may constitute a counterelectrode for the discharge system and the arrangement has been found to give excellent results when broad surfaces of a workpiece are to be coated. The discharge electrode is a needle spaced from the frangible foil while the discharge chamber is provided as a discharge gun whose barrel is trained upon the workpiece and receives, at an intermediate location between the mouth of the barrel and the spark-discharge shock-wave generator, a mass or body of particles to be propelled against the workpiece.

I pointed out further in application Ser. No. 574,056, that the discharge system may be constituted by a fusible wire which explosively disintegrates upon the application of a high-energy electrical pulse therethrough to form a spark-type discharge in the gap vacated upon fusion of the wire. Alternatively the detonation source may include a pair of electrode elements adapted to define between them an electrical discharge gap, the pulverulent material being disposed in close proximity to the gap and advantageously surrounding it. The gap may be bridged temporarily by a fusible element which is disintegrated upon discharge of a high-energy pulse across the gap, the fusible element serving to lengthen the effective time of discharge as a consequence of the delayed opening of the gap.

In application Ser. No. 696,757, it is pointed out that heated particles may be projected against a workpiece and that the particles can be formed in situ within the barrel of the discharge chamber by thermal destruction of a fusible material, the thermal destruction being effected by electrical disintegration or erosion of the fusible element by hot gases, preferably in a plasma condition.

A pair of particle-forming electrodes may be provided at a location ahead of the discharge electrodes and may be heated by electrical resistance or arc-forming techniques to vaporize the metal of at least one of the electrode to produce particles which are totally gaseous or upon condensation or solidification at the temperature within the discharge chamber, are in a liquid or finely divided solid state.

In effect, the particle cloud is a condensate of a particle size substantially smaller than that of particles of similar materials made by mechanical comminution techniques.

Still further uses of high-energy spark discharges and explosive discharges with the aid of fusible electrodes are described in application Ser. No. 735,760 which deals with a hydroimpact-forming system in which a column of liquid in a barrel of a shock-forming gun is trained upon the workpiece and an explosive-type discharge is effected in the column to propel the column against the workpiece and generate a shock wave superimposed on the gross movement of the liquid to shape the workpiece. The liquid is preferably directed at the workpiece in a jet with a velocity of 100 to 10,000 m./sec. and the discharge is superimposed impulsively on this jet.

It has been found in accordance with these teachings, that it is possible to selectively shape large-area metallic bodies or selectively to apply high-energy-rate forces to selected regions of a body to be deformed by training at the workpiece, from a location spaced therefrom, a discharge chamber whose barrel receives a liquid column which is propelled at least in part by an electric-discharge-induced shock wave against the workpiece surface.

When a column of liquid is trained in this fashion upon a limited region of a workpiece and is constituted as a dynamic force-transmitting medium, such that it is actually propelled against the surface rather than being confined to the function of shock-wave-transmitting medium, highly improved accuracy can be obtained in conforming the workpiece to a die over the accuracy which is possible using systems with a relatively static liquid medium filling a closed space and in force-transmitting relationship with the workpiece.

The mouth of the barrel and indeed, the liquid level therein is located below or at a distance from the workpiece surface so that an ambient gas fills the space between the liquid in the barrel and the workpiece. A number of such barrels, provided with means for refilling the barrel chambers with a liquid dielectric, are trained at respective regions of the workpiece or the discharge gun is constituted as a swingable member adapted to sweep its impact across the surface. Advantageously, the means for refilling the barrel may also be used for delivering liquid to the latter at a rate sufficient to produce a high-velocity jet contacting the workpiece even in the absence of impulsive or shock-wave force. This stream may be continuous and/or pulsed to coincide with the electrical discharge.

BACKGROUND OF THE INVENTION

The instant invention is based upon the aforementioned applications and knowledge in the art that it is possible to shape a workpiece with a liquid-transmitted shock wave produced in part by an impulsive discharge in or adjacent the liquid medium. Thus the prior art has recognized, even before the developments set forth in the copending applications mentioned above, that it is possible to shape a workpiece with the aid of a shock wave produced by spark discharge and wherein the shock-wave-transmitting medium consists of a liquid which may be a dielectric in cases in which the discharge energy is to be heightened.

OBJECTS OF INVENTION

It is the principal object of the present invention to provide an improved system for the spark forming of a workpiece in which the discharge energy transmitted to the workpiece is increased and control of the discharge facilitated.

A more specific object of this invention is to provide an improved method and apparatus for controlling the hydroimpact high-energy-rate forming of plastically deformable bodies with respect to the directional effects of the high-energy-rate forces.

Yet a further object of this invention is the provision of an improved electrode system and method of operating same, for use in spark shaping, coating and forming of metallic and other workpieces.

Another object of the instant invention is to extend the principles set forth in the above-mentioned copending applications and generally to improve the high-energy-rate shaping, coating or forming of plastically deformable workpieces.

It is still further an object of this invention to provide a method of and an apparatus for the efficient, accurate and economical shaping of plastically deformable bodies of large surface area and complex configuration as well as the shaping of workpieces requiring higher shaping energy in certain regions than in others.

Still another object of this invention is the provision of a system for the shaping of metallic and other plastically deformable bodies in selected areas without undue concentration of shaping pressures and forces which may result in tearing and deterioration or undesirable stress of the workpiece.

Still another object of the instant invention is to provide a hydroimpact device with repetitive triggering for the shaping or working of large-area plastically deformable or frangible workpieces in accordance with a predetermined program and with optimal force application to selected areas of the workpiece.

SUMMARY OF THE INVENTION

These objects, and others which will become apparent hereinafter are attained, in accordance with the present invention, in a "spark-forming" or high-energy-rate machining apparatus in which an improved electrode system is provided to increase the available forming energy or power and to control the development of the discharge, whether the device is used to produce a shock wave for static transmission by a fluid or for the dynamic hydroimpact system described above, an improved control arrangement in the barrel of a hydroimpact-forming system for controlling the localized application of forming pressure, a system for programming the improved control device, and an improved power supply which has been found to increase shaping accuracy, especially when used with a fusible conductor gap-firing arrangement as will be described in greater detail below.

When the term "spark forming" is used herein, therefore, it will be understood that to the extent that the invention applies to an improved electrode system for generating the shock wave, the expression may refer to spark discharge methods and apparatus in which a particulate material is carried by the shock wave and bonded to a substrate through a gaseous medium, to a system in which a spark-generated shock wave is transmitted to the workpiece surface by a static liquid medium in contact therewith or to a system in which a circulated liquid substantially completely filling the space between the discharge and the workpiece, and to hydroimpact systems in which the shock-wave-transmitting medium is a moving column of liquid. When, however, the invention pertains to directional control and the programming of hydroimpact arrangements, the term "shock forming" may be used exclusively in connection with such systems.

According to the principal aspects of the present invention, which makes use of principles described in the above-mentioned application, shock forming, i.e., the application of one body to another in bonding relationship, the shaping of a body or the coating of a substrate with a particulate material, is carried out with a shock-wave-transmitting medium between a workpiece (e.g., a substrate or a plastically deformable metallic or nonmetallic body which may overlie a die cavity) by producing a spark discharge in a fluid medium. The invention makes use of my discovery that an improved utilization of the electrical energy and improved control of the discharge may be obtained when the discharge gap includes a fusible conductor which is explosively disintegrated by the application of a high-energy electrical pulse thereacross. A system using a fusible conductor is described and claimed in application Ser. No. 311,061 issued as U.S. Pat. No. 3,267,710, and the applications which are mentioned above and have extended the principles set forth in this application and its parent case. More specifically, it has been pointed out in my prior work in this field that an extended discharge with higher useful energy, i.e., a greater efficiency of conversion of the electrical energy into useful work in form of a shock wave, may be obtained with an electrode system in which a flexible conductor is fed toward a relatively massive electrode and is consumed by the discharge so that an increasing gap is formed with the massive electrode at which the final discharge is sustained. At the conclusion of this discharge, another length of fusible conductor may be fed through an opening in one, or both of the spark-discharge electrodes, the spark being initiated by the advance of the fusible wire or the external switching of a high-energy source, e.g., a capacitor, across these electrodes. Such systems have, however, the disadvantage that the final discharge, after the destruction of the fusible conductor, causes a deterioration, welding or the like of the main electrodes and, especially the electrode through which the fusible conductor is fed, thereby blocking the channel and obstructing the passage through which further control feed must occur. Moreover, control of the breakdown point, when the advance of the conductor is used as a switching action, high-rate repetition of the discharges and the like are restricted.

The present invention provides an improved electrode system for discharge forming, in which a fusible conductor is fed toward a discharge electrode of the spark discharge system; the fusible conductor is provided adjacent the path of the main discharger and in spaced relationship therewith so that the conductor is not fed through the electrode but past the latter.

More specifically, a guide-and-feed means is provided for a continuous length of the fusible conductor or pieces of fusible conductor, in line with which the relatively massive electrode is provided, the fusible conductor being fed in a straight or curved path toward the latter. Alongside this path, preferably at an adjustable distance therefrom, there is provided the second electrode in spaced relationship with the fusible conductor so that two discharge gaps may be formed, namely, between the stationary massive electrode and the fusible conductor and between the fusible conductor and the other electrode alongside its path. The fusible conductor may be a rod, wire or band and, in accordance with a further feature of this invention, the latter may be bent transversely of its direction of feed to stiffen the conductor.

The permanent electrodes are formed, at least at their tips, of a material which resists discharge erosion, e.g., of a copper-tungsten or silver-tungsten alloy.

Yet another feature of this aspect of the invention resides in the initiation of the discharge by the advance of the fusible conductor and the provision of the fusible conductor as pieces of wire, foil or the like which are periodically or aperiodically fired into the gap between the permanent electrode members, one of which may be in the path of the projected piece of fusible conductor while the other is spacedly disposed alongside this path. Most desirably, the latter electrode is a rod, strip or the like extending transversely to the fusible conductor or its path and preferably at right angles thereto, although the laterally offset electrode may also extend at an acute angle to the path, preferably in the direction of feed of the fusible conductor.

All three of the critical elements of this electrode system, namely, the electrode in the path of the fusible conductor, the fusible conductor itself and the laterally offset conductor adjacent the path, may be shiftable toward and away from one of the other elements to control the intervening gap and thereby initiate the discharge when the surrounding medium is, for example, a liquid dielectric.

According to another aspect of this invention, a hydroimpact, shock-wave-transmitting column of liquid, preferably in the form of a high-velocity stream is directionally controlled by providing along the jet at least one transverse control jet which is employed to deflect the main high-energy-rate liquid column. This aspect of the invention is based upon the discovery that fluidics techniques can be used most effectively to accomplish a directional regulation of a high-velocity stream of liquid upon which the shock wave is superimposed so that bodily swinging, displacing or otherwise modifying the position of the barrel of the hydroimpact is no longer necessary.

The invention makes use of principles originally set forth in application Ser. No. 735,760 for the shaping selectively of large-area bodies and enables control of the high-energy-rate forces applied to selected areas of the body. More specifically, it has been found that by analogy to the electromagnetic deflection of an electron beam in high-energy cathode-ray or other vacuum tubes, a high-velocity liquid stream upon which the shock wave is superimposed can be deflected with respect to its effective center of force by providing along this tube and preferably close to the point at which the liquid stream enters the tube, one or more control jets oriented generally transversely to the main stream. The effectiveness of such control jets is most surprising when it is considered that propagation of the shock wave in a liquid medium is generally omnidirectional. The use of a control jets in accordance with the present invention, however, allows selective impingement of the forming wave at predetermined areas of the workpiece. The invention is applicable to systems in which a liquid stream is constituted as a dynamic force-transmitting medium which is actually propelled against the workpiece surface rather than merely constituting a static medium through which the shock wave is transmitted. It is possible in accordance with the present invention to operate selectively on large areas of a body or apply selectively high-energy-rate impacts at selected regions without displacement of the barrel and preferably with the barrel stationary. A plurality of control nozzles are preferably provided adjacent the inlet orifice of the barrel which in accordance with this invention has a cross section smaller than the cross section of the barrel in the region of the control nozzle and at its mouth so that each of the nozzles is trained transversely of the shock-wave stream. The control fluid may be gas or liquid and is delivered at a pressure which may range from one-tenth to one-fiftieth of the pressure of the shock liquid.

According to a more specific feature of this invention the control nozzles are operated by a programming device in order to apply predetermined shock-wave pulses to preselected regions of the workpiece and prevent overstressing of the most sensitive areas. My present invention also applies an adaptive control system in which the response of the workpiece to the shock-wave stream is sensed and the direction, intensity and duration of the shock pulses controlled to optimize forming of the workpiece. The sensing means may respond to the rate of displacement of the workpiece into the die cavity as well as the degree of such displacement.

A further aspect of this invention resides in the provision of an energization circuit for fusible-conductor gap-firing arrangements in which both a high-energy and low-energy discharge network are connected across the spark gap, a low-capacity high-voltage capacitor being used to fire the gap whereupon a low-voltage high-amperage source sustains the discharge.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a diagrammatic vertical cross-sectional view of an apparatus for the hydroimpact forming of a workpiece into a die cavity, in accordance with the present invention;

FIG. 1A is a horizontal section through the barrel of the system of FIG. 1 taken along the line IA--IA of FIG. 1 but showing a modified programming system;

FIG. 1B is a diagrammatic cross-sectional view of a sensor system for detecting the displacement of the workpiece using the system of FIG. 1A;

FIGS. 1C and 1D are block diagram representing alternative programming arrangements for the system of FIG. 1A;

FIG. 1E is a diagram of a system responsive to the parameters of the shock-wave-transmitting liquid and adapted to be used with the system of FIG. 1A;

FIG. 2 is a vertical section representing a detail of the electrode system of FIG. 1;

FIGS. 2A-2D, 2A'-2D' and 2A"-2D" represent various operating modes of the system of FIG. 2, in accordance with the present invention;

FIGS. 3 and 4 are sectional views through a hydroimpact barrel diagrammatically illustrating a modification of the electrode system, in accordance with the present invention;

FIGS. 5A, 5B, 6A and 6B illustrate other modes of operating the electrode system of FIG. 2;

FIG. 7 is a diagrammatic sectional view of an apparatus in which individual lengths of fusible conductors are introduced into the discharge gap, according to the present invention;

FIG. 7A shows another means for introducing conductors into the gap;

FIG. 8 is an axial cross-sectional view showing another control system in accordance with the present invention;

FIG. 9 is a detail view illustrating a modification of the control system of FIG. 8;

FIGS. 10 and 11 are diagrams showing a control arrangement for the shaping of large-area bodies, in accordance with this invention;

FIGS. 12, 13 and 14 are circuit diagrams illustrating improved supply arrangements for the high-energy-rate-forming arrangements of the present invention;

FIG. 12A is a graph illustrating the voltage waveforms obtained with the circuit of FIG. 12;

FIG. 13A is a detail of a modification of the system of FIG. 13;

FIG. 15 is a diagrammatic elevational view of another electrode system according to this invention;

FIGS. 16A and 16B are opposite end views of the control-guide arrangement of FIG. 15;

FIG. 17 is a view similar to FIG. 15 illustrating another embodiment; and

FIG. 18 is an end view of the conductor used in the system of FIG. 17.

SPECIFIC DESCRIPTION

In FIG. 1, I show a system for shaping a workpiece 10 to the configuration of a die cavity 11 in a die 12 with which the workpiece, here a sheet-metal body, is juxtaposed so as to overlie the cavity. A retaining ring 13 may serve to hold the workpiece 10 in place.

The workpiece is forced to conform to the contours of the die cavity 11 by a jet 14 of liquid which is propelled at high velocity through the barrel 15 and upon which is superimposed a shock wave by a discharge generator generally represented at 16 in FIG. 1. The shock-wave generator comprises a housing 17 in line with the barrel 15 and having a forwardly converging wall 17a open at an orifice 17b coaxial with the barrel 5 but of a cross section which is substantially less than that of the barrel. The latter has an open mouth 15a wider than the orifice 17b and trained upon the workpiece 10.

Liquid, preferably water or a dielectric such as kerosene or transformer oil, is supplied at high velocity to the chamber 17c of the shock-wave generator 16 by a pump 18 drawing upon reservoir 19 and controlled as represented by the unit 20. A pressure-relief valve serves to bypass excess liquid to the reservoir 18. While the control 20 is shown to be connected to the pump 19 so as to regulate the rate of fluid flow into the chamber 17c, it will be understood that it may be additionally or alternatively connected to the valve 21 to regulate the pressure of the liquid within the chamber 17c and, therefore, the head with which it emerges from the orifice 17b.

While the spark discharge assembly of the system of FIG. 1 is shown only diagrammatically, and in structural detail may be constituted as shown in FIG. 2 and may operate in the modes described in connection with FIGS. 2A-2D, 2A'-2D', 2A"-2D", FIGS. 5A, 5B, 6A and 6B, it may also have the configuration set forth in connection with FIG. 7 or FIG. 7A so as to be fired by introduction of the piece of fusible conductor into the gap and the energization circuit described in connection with FIGS. 12, 13 or 14.

The shock-wave generator of FIG. 1 includes a source 22 of a relatively thin fusible conductor 23 in the form of a rod, wire, band or strip, which is fed toward an electrode 24 in its path by a motor 25 or other feed means under the control of a start-stop regulator 26. The advance of the further electrode 27, which extends transversely to the fusible wire 23 and is spaced therefrom by a gap G, is regulated by a motor 28 whose pinion 28a meshes with the rack 27a forming part of the electrode 27. Another motor control is provided at 29 for the motor 28.

A discharge may be provided across the gap between the mutually insulated permanent electrodes 24 and 27 by a capacitor 30 which can be charged by DC source 31 through the usual charging resistor 32 in series with a reverse-surge-suppressing choke 33 upon the closure of a switch 34 by a programmer 35 which, in turn, operates the control units 20, 26 and 29.

To provide directional control of the liquid jet (forming or power jet) 14 propelled at high velocity against the workpiece 10, the barrel 15 is provided with a fludics system under the control of the programmer 35 and represented diagrammatically in FIG. 1. A number of angularly equispaced nozzle arrays may be provided at 36a, 36b and 36c at various angles of intersection with the axis of the barrel 15 and the main direction of the liquid stream 14, but all generally transverse to the latter and fed by respective control valves 37 which are operated by the programmer 35 via a valve control unit 38. The valve 37 is supplied with control jet fluid, e.g., gas or liquid with a pressure between 0.1P and 0.05P (where P is the pressure of stream 14 upon emergence from chamber 17c) by a pump 39. The latter draws fluid from the reservoir 19, excess fluid being returned by the pressure-relief valve 39a.

FIG. 1A shows a suitable programming arrangement for one of the sets of control nozzles, the control jets of which sweep the main forming stream across the workpiece in a programmed manner, the system of FIG. 1A being of course employed in conjunction with that of FIG. 1, when for example adaptive control is desired. The barrel 15 of FIG. 1A is shown to be provided (in a plane perpendicular to the axis of this barrel and parallel to the plane of the paper) with an array of nozzles 36a including the sets of diametrically opposite nozzles 36a.sub.1, 36a.sub.1 ', 36a.sub.2 , 36a.sub.2 ', 36a.sub.3, 36a.sub.3 ', 36a.sub.4, 36a.sub.4 '. Each of these sets of diametrically opposite nozzles may receive jets moving in opposing directions or in the same direction as shown in FIG. 1B, a drain being provided at 15b (FIG. 1) when opposing jets only are used and the deflection of the main stream 14 is to be controlled only by the relative intensities of the control jets or their presence or absence.

Each pair of nozzles of each array in the system of FIG. 1B is shown to be provided with a valve 37 of the type described in connection with FIG. 1 and located between the pump 39 and the barrel 15. In this arrangement as well, the pressure-relief valve 39a is connected across the pump 39 which draws fluid from the reservoir 19 and returns fluid to the latter via line 39b.

Each valve 37 is energized by comparator circuits 38a of the programmer which may be solely controlled by a memory or stored inputs represented by the taped storage assembly 38b. Preferably however, a clock pulse is provided at 38c to the comparator 38a which compares the input from the synchronized tape 38b with inputs representing the degree of deflection of the workpiece 10 into the die cavity 11 and the force applied to the workpiece, e.g., by a matrix of feelers 38d in the mold cavity 11. As shown in FIG. 1B the feelers 38d, which have no effect on the shape of the mold and are merely pushed inwardly by the deflection force applied at F and F' to the workpiece, constitute armatures shiftable in respective electromagnetic coils 38e and generate an output indicating the rate of displacement of the respective feelers and thus the rate of deflection of the workpiece at each location, as well as the position of the feeler, representing the degree to which the workpiece has been deflected. This feeler matrix constitutes an input to the programmer 38a which in turn controls the valve 37 to produce the desired workpiece configuration with the preprogrammed rates of deflections of the various portions as represented by the storage or memory 38b.

An alternative arrangement is shown in FIG. 1C wherein the comparator 38a receives inputs from the magnetic memory 38b' and from the matrix 38d scanned by the clock pulses from a source 38c to produce outputs controlling the pressure and velocity of the liquid stream 14 as represented at 20, the discharge energy of the shock wave as controlled by the programmer 35 by the degree to which line 40 permits capacitor 30 to charge, and the jet direction via the control nozzles 36a, 36b and 36c as represented by the unit 37 in FIG. 1C.

In the modification of FIG. 1D, the entire workpiece-forming process is preprogrammed at 35a and is triggered by the clock pulses from source 35b to operate the controls 20, 40 and 37 mentioned earlier. For further adaptive control of the process, an additional feedback may be provided as represented in FIG. 1E wherein a pitot-tube arrangement is shown at 15c in the barrel 15 to feed back a signal representing the velocity of the jet 14 to the programmer board.

In operation, the advance of the wire length 23 (FIG. 1) to reduce the gap G' between it and the electrode 23 in its path and/or the advance of the electrode 27 to reduce the gap G between this electrode and the fusible conductor 23 results in a breakdown of both of the gaps G and G' to enable the capacitor 30 to discharge massively through the conductive path formed by the electrode 24 the gap G', the length of fusible conductor 23 between the electrodes 24 and 27 and the gap G to consume the fusible conductor.

Thereafter the discharge bridges the electrodes 24 and 27 as will be described in greater detail hereinafter. The discharge is of an explosive nature and generates a shock wave which is superimposed upon the forcible ejection of the liquid stream represented at 14 so that the liquid impinges upon the workpiece 10 and forces it into the die cavity 11 and the impulsive discharge is predominantly directed toward the orifice 17b by the walls of the chamber 17c.

The control chamber defined by the barrel 15 ahead of the orifice 17b is provided with the nozzles 36a and 36c through which a control fluid, in this case the same fluid as constitutes the forming stream, is injected transversely to this stream to deflect the direction of the shock impact interacting with the power jet to sweep the latter along and selectively form the workpiece under the control of the programmer.

As shown in FIG. 1 a control-nozzle arrangement may comprise three arrays of control nozzles 36a, 36b, and 36c which are directed at different angles to the axis of the power jet and, for example, the first array 36a may have its nozzles inclined relatively upwardly while the second array is directed perpendicularly to the forming jet and the third array is inclined inwardly and downwardly, each of the nozzles of each array being provided with a respective valve arrangement.

It has been found that the location at which the power jet and the shock wave superimposed thereon is effective, the spread of the shock wave and power jet and therefore its intensity and even the rate of forming of the workpiece may be controlled with great precision for repeated operations in a predetermined pattern or program. The programmer 35 illustrated in FIG. 1 selects one or more of the control-jet nozzles for interaction with the individual power jet pulses in accordance with the present invention.

In FIG. 2 there is shown the spark generator for the apparatus of FIG. 1. The generator 16 comprises an electrode 24, here formed as a rod extending through an electrically insulating bushing 17d whose head 17e is held in the wall of this bushing by a clamping ring 17f bolted to the outer wall of the housing 17.

The electrode 24 is held in a chuck 24a of a piston-and-cylinder arrangement mounted in a housing 17q of the chamber 17 and including a fixed double-acting cylinder 24b the fluid ports of which are connected to a control-valve arrangement 24c regulating the advance or retraction of electrode 24. The piston 24d of this arrangement carries the chuck 24a and is shiftable to the left to reduce the gap G' or to the right to increase this gap under the control of the programmer 35 which is connected to the control unit 24 in the usual manner. The wiper 24e engages rod 24 and has a terminal 24e' traversing the feedthrough insulator 17h of the housing 17j and connected to the power supply which is provided with the battery 31, the switch 34, the choke 33 and the charging resistor 32 previously mentioned. In this embodiment however, the capacitor 30 may be connected in series with a switch 30a and the electrodes so that the gap may be fired by breakdown induced by movement of the electrodes or the fusible wire or by closing switch 30a, in the alternative. Switch 30a may also represent an adjustable breakdown gap designed to trigger automatically with the buildup of a sufficiently high potential across the electrode system.

The fusible wire 23 is fed to the gap through an insulating sleeve 17j in the housing 17 aligned with the electrode across a diameter of the chamber 17j while the further electrode 27 is disposed axially below the fusible wire 24 across the gap G. A housing 22a is affixed to the chamber 17 and receives the supply reel 22 from which the continuous length of fusible wire is led into the insulator 17j between a pair of feed rolls 22b which may be of a profile corresponding to that of the fusible conductor as described in connection with FIGS. 15-18. The feed rolls 22b are driven by the motor 25 under the control of unit 26 as mentioned earlier.

The electrode 27 extends through the upright insulator 17k and is held in a chuck 27a of the piston 27d of a piston-and-cylinder arrangement similar to that described in connection with electrode 24. The cylinder 27b is anchored in the housing 17m which has a feedthrough insulator 27e' carrying the wiper 27e engaging electrode 27 and forming the other terminal of the power source.

In a first mode of operation (see FIGS. 2A-2D), control unit 24c is operated to controllably position the electrode 24 at a fixed distance d from the point of intersection p of an imaginary extension of electrode 27 and the axis A of the fusible wire 23, the path of which is illustrated in dash lines in FIG. 2A. The conductor 23 is then fed until it contacts electrode 24 whereupon a circuit is closed with a signal generating circuit 41 to trigger the programmer and deenergize motor 25 of control 26. The position of the fusible wire 23 is then as shown in FIG. 2B and no gap G1 is employed. In the third stage of the triggering of the discharge the distance D between the electrode 27 and the fusible wire 23 is reduced by advance of the electrode 27 (FIG. 2C) until the breakdown gap distance G is reached whereupon a discharge develops between the electrode 2 and the fusible wire 23 drawing current from the capacitor in effectively a short-circuit condition to yield an explosive discharge which consumes the length d of the fusible wire and thereafter is transformed into a direct discharge between electrodes 24 and 27 (see FIG. 2D). Of course, this arrangement requires omission of switch 30a of its closed condition during the entire operation.

In a second mode of operation, using basically the same system, electrode 27 is advanced to the predetermined gap distance G from the fusible wire 23 (FIG. 2C) while switch 30a remains open to allow the potential in capacitor 30 to charge above the breakdown level of this gap. The switch 30a is then closed to create the incipient discharge across the gap G, whereupon a full explosive discharge flows as shown in FIG. 2D.

In a third mode of operation, also using the basic system of FIG. 2, the first step, as represented by FIG. 2A', fixes the desired length of the fusible conductor at d-g where g is a fixed gap to be maintained between the fusible wire 23 and electrode 24 while d is the spacing along the path of advance of the fusible conductor between electrode 27 and electrode 24. In this case, the fusible conductor 23 is advanced until the spacing of gap G' has the dimension g whereupon a signal is transmitted to the motor 25 to terminate advance of the fusible wire. To this end, the detector 41' may be a resistance bridge in which one arm is formed by the conductivity cell constituted by the electrode 24, the fusible wire 23 and the gap G'. While the predetermined gap spacing G' is maintained, the electrode 27 is advanced (switch 30a being closed) until discharge is simultaneously formed across the gaps G and G' by breakdown of the fluid (FIG. 2C'), whereupon a substantial short-circuit condition develops across the capacitor 30 to yield the explosive discharge consuming the fusible conductor and bridging the electrodes 27 and 24 (FIG. 2D').

An alternative to this mode of operation follows the steps set forth until the electrodes and the fusible conductors are in the position illustrated in FIG. 2C' while the switch 30a is open and thereupon closes switch 30a to produce the breakdown initially across the gaps G and G' and finally across the space between the electrodes 24 and 27 as shown in FIG. 2D'.

A further mode of operation is illustrated in FIGS. 2A"-2D". In this system, the motor 25 is controlled to advance the fusible conductor 23 through a fixed length l, whereupon the gap G' has a gap width g which may be undefined. In this case, the consumed length of electrode will as a practical matter be equal to l. Here too, l is less than d or l.apprxeq.d-g and upon advance of the fusible conductor 23, the electrode 27 may be advanced (FIG. 2B") to produce the incipient spark discharges shown in FIG. 2C" and thereafter the explosive discharge between the electrodes as represented in FIG. 2D".

In FIG. 5A, there is shown another mode of operation in which the electrode 27 is brought into a position just adjacent the path of the fusible conductor 23 or into contact therewith as the fusible conductor is advanced across this path. When the fusible conductor then reaches a point at which breakdown occurs in the gap G', the extended length l of the fusible conductor is consumed and the discharge bridges the electrodes 27 and 24. The electrode 24 can be advanced after the conductor 23 has been fixed to fire the discharge across the gap G' as well or both fusible conductor and electrode can be moved relatively to initiate discharge.

In a further mode of operation illustrated in FIGS. 6A and 6B, the length of fusible wire 23 is first pushed ahead of the electrode 27 and in contact therewith (FIG. 6A) or with a predetermined spacing therefrom over the gap G and the other electrode 24 is advanced toward the fusible wire 23 until the width g of the gap G' is such as to enable the system to fire, thereby consuming the conductor and producing the discharge illustrated in FIGS. 2D, 2D' and 2D".

As can be seen from FIGS. 3 and 4, the electrodes 24' and 27' can lie in a common plane perpendicular to the axis of the power jet and including the fusible wire 23' which is here fed diametrically. In FIG. 4, the electrode 27" is shown to extend at an acute angle to the fusible wire 23" in the direction of feed.

FIG. 7 shows an arrangement in which pieces of fusible conductor, e.g., as shown at 123 are supplied to the gap between an electrode 124 in the path of this conductor and an electrode 127 extending transversely to this path. The pieces may be flat leaves, pencillike sections of rod or the like and are stacked as shown at 123' in a magazine 122 from which they are successively driven into the space between the electrodes 124 and 127 by a plunger 125 which may be triggered by a control 126 coupled with an electromagnetic coil 125a diagrammatically shown to surround a portion of the plunger 125. The pieces 123' are stacked vertically in the magazine, although it is also possible to insert them laterally as shown for the fusible conductor section 123" and as represented by the arrow 123a". A spring 125b tends to draw the plunger 125 out of the magazine 122 which may have its successive tiers alignable with an insulating guide sleeve 117d formed in the chamber 117 or may be permanently aligned with this guide sleeve so that each of the pieces 123' or 123" is aligned with the sleeve in turn.

The electrode 127, which may be vertically shiftable in the insulating sleeve 117n as shown in FIG. 2 to set the desired gap distance G between its free end and the path of the fusible wire 123, is connected to one terminal of a power supply which consists of a battery 131 adapted to charge the capacitor 130 through a resistor 132 in series with a surge-suppressing choke 133. A switch 134 may be left closed in order to permit the capacitor 130 to charge immediately after extinction of the discharge across the electrodes 124 and 127. Electrode 124 may also be shiftable in a guide sleeve 117j to set the position of its free end in the path of the fusible wire 123.

The chamber 117 may open against the workpiece 110 as shown in FIG. 1 via a barrel provided with control jets or, as illustrated in FIG. 7, may be supplied with a dielectric liquid by a pump 118 via a flow-control valve 118' from a reservoir 119 while a pressure-relief valve 121 is connected between the output of the pump 118 and the reservoir. Return of fluid to the reservoir is effected via line 117b.

A switch 130a may be provided in the discharge circuit while the workpiece 110 is juxtaposed with a die cavity 111 and held in place between the die 112 and the body of chamber 117.

The gap of the system shown in FIG. 7 can be fired by propelling the lengths of fusible wire 123 in succession between the electrodes 124 and 127 after each preceding discharge has quenched. Alternatively, a sequencing arrangement may be used to first fire the length of fusible conductor 123 into the gap and thereafter close switch 130a to produce the discharge. The system basically operates in the manner previously described.

It will be understood that the system of FIG. 7 may be provided with the circuits shown in FIGS. 12-14 and that fusible conductor 123 may be fired into the gap through contoured guide sleeves as shown, for example, in FIG. 15. Control arrangements of the type illustrated in FIG. 10 may of course also be used and a number of discharge tubes with a single-spark generator may be provided as described in connection with FIG. 11.

In FIG. 7A, there is shown a modification in which the magazine 222 of the system of FIG. 7 is a barrel which may be carried by the shaft 222a and stepped by a pawl-and-ratchet mechanism 222b while the plunger 225, operating as described in connection with FIG. 7, propels the pencil-shaped length of fusible wire into the gap between the electrodes. The barrel 222 is then provided with chambers 222b in angularly equispaced relationship about the shaft 222a and adapted to receive the lengths of fusible wire and then align themselves with the guide sleeves 117d.

The system of FIGS. 7 and 7A may thus be operated in several modes. In a first mode, the chamber 117 is completely filled with liquid and holds the workpiece in an original configuration without deformation or provides a low-forming-rate force to the workpiece, whereupon the discharge is triggered by firing the length of fusible conductor into the gap to plastically deform the workpiece to the extent determined by the generated shock pressure. The introduction of further lengths of fusible conductor into the gap will produce successive discharges as required. In a second operating mode, the workpiece is preformed by increasing the hydraulic pressure within the chamber and final shaping is effected by one or more spark discharges. In a third mode of operation, the liquid level is located below the workpiece surface so that a closed space is provided which may be filled with air or is evacuated, the discharge between the electrodes propelling the liquid mass at high velocity toward the workpiece. Finally, a high dynamic flow of fluid can be provided within the chamber 117 upon which the discharge is superimposed.

In FIGS. 8 and 9, there is shown a system for the adaptive control of hydroimpact forming, the expression being used here to refer to shaping, cutting, crushing, cladding (the application of a layer or foil of a metal to a metal substrate), lining, forging or stressing of a workpiece in which a column of liquid is projected in the direction of the workpiece, here represented diagrammatically at 310. The apparatus comprises a shock generator 317 provided with a pump 318 adapted to produce a high-velocity stream of liquid in the direction of the workpiece, the liquid being drawn from a reservoir 319. The upper end or mouth of chamber 317 narrows into an orifice 317b which is surmounted by a barrel 315 defining a first control chamber C.sub.1 and widening at 315a into a discharge mouth forming a second control chamber C.sub.2.

A discharge electrode system, which may have the configuration shown in FIG. 2, is provided in the lower part of chamber 317 as illustrated generally at 316. This generator may include an electrode 324 mounted in insulated relationship on the wall of chamber 317 in the path of a fusible wire 323 fed from a reel 322 in the direction of the electrode 324. Transversely of the fusible conductor 323, there is provided a further electrode 327 which may be advanced and retracted by a motor 328 via a rack-and-pinion arrangement represented diagrammatically at 328a. A power supply of the type shown in FIG. 2 or FIGS. 12-14 may be connected to the terminals 330b.

As described in connection with FIG. 1, the first control chamber C.sub.1 may be provided with arrays of control-jet nozzles 336a and 336b respectively inclined upwardly and downwardly to the axis of the column of liquid projected against the workpiece 310. The control jets 336a, 336b permit deflection of the power jet or shaping of the latter, e.g., to render it more divergent or more concentrated as required, and also control of the velocity and energy of the power jet. In addition, the adaptive control system of FIG. 8 provides an adapter 345 in the chamber C.sub.2 which is axially shiftable as shown in two further positions by phantom lines, via a solenoid or hydraulic servo 345g. The outer contours 345b of this adapter body conform to those of the wall 315a of chamber C.sub.2 and define the cross section of the power jet. Preferably, the chamber C.sub.2 is cup or bowl shaped while the body 345 has the configuration of a cone.

By moving the body 345 in and out in accordance with a predetermined programmer under the control of sensors as described in connection with FIG. 1A, it is possible to concentrate the force of the power jet in concentric circles as represented at 345c, 345d and 345e and this arrangement may be used, for example, when the workpiece is to be shaped in a die having an annular groove. If the annular groove is of uniform width and depth, the location of the adapter cone in the chamber C.sub.2 can be adjusted such that the output jet has an annular width substantially equal to that of the annular groove when it impinges upon the workpiece surface. The control nozzles 336a, 336b are then able to regulate the velocity, volume and effective force of the jet to suit the depth of the die groove and the workpiece material so that deformation occurs without damaging the die or the workpiece. Alternatively, the adapter 345 is shifted in and out to sweep the power jet across the annular path. By suitable selection of the configuration of the adapter and the chamber C.sub.2, practically all workpiece configurations can be formed with ease and accuracy.

When the die, e.g., 412 has an intricately shaped cavity 411 as shown in FIG. 9, the workpiece 410 is given a preliminary configuration or preshape so as to generally conform to the die cavity, e.g., by increased hydraulic pressure in a system of the type shown in FIG. 7, to the extent that portions of the workpiece bottom on the ridges of the contour 411 of the die. By then providing an adapter body or adapter bodies of suitable shape, e.g., as shown at 445, it is possible to split the power jet into a plurality of discrete power jets whose velocities, volumes and cross sections may differ but are determined in accordance with the degree to which the workpiece must be deformed and the nature of the contours. Alternatively, control jets may be used as described above to direct the power jet to selected areas and then regulate the parameters of the power jet in accordance with the forming requirements of the particular workpiece.

FIGS. 10 and 11 show an arrangement in which a plurality of hydroimpact guns or barrels 515a, 515b . . . is provided in an array covering the entire area of a die cavity 511 formed in the die 512 overlain by the workpiece 510. The barrels 515a, 515b . . . are trained upon the workpiece and may have a common spark-discharge chamber 517 provided with respective sets of electrodes 524 and 527, a common pump 518 and reservoir 519, but individual reels 522 supplying the fusible wire 523 to the respective electrode gaps. The electrodes are connected to power supplies as set forth in connection with FIGS. 12-14 via the terminals 430b. Each of the barrels 515a, 515b . . . is provided with three sets of control-jet nozzles 536a, 536b and 536c, each having respective control valves 537 operated by a corresponding control 538 from the master computer control 535. The barrel are operated in sequence with dynamic parameter control of the liquid columns as described above in adaptation to the particular configuration of the workpiece desired.

The power supply or circuit shown in FIG. 12 may be used for the electrode systems of FIGS. 1-11 and basically comprises a dual arrangement including a high-voltage breakdown power supply which may deliver relatively little current and, consequently, low-power, and a low-voltage power supply capable of delivering high current to sustain the discharge and provide the major portion of the power. Of course, an intermediate supply network may be used to bridge the voltage pulse envelopes of the high-voltage and low-voltage supply network. Thus the circuit shown in FIG. 12 is provided with an electrode 627 and an electrode 624 adapted to be bridged in part by a fusible wire 623 fed through a guide 617j by a motor-and-feed means not further illustrated in this Figure. As noted above, the advance of one or both of the electrodes and/or of the fusible wire may be used to trigger the discharge.

The high-voltage power supply makes use of a high-voltage capacitor 630' connected in series with a high-voltage DC source 631', e.g., of a potential above 1,000 volts, which is connected across the capacitor through a surge-suppressing choke 633' and a charging resistor 632'.

In the discharge circuit of the capacitor 630', there is provided a switch 630a' controlled by a breakdown detector 630b' to cut off the high-voltage capacitor as soon as the main power discharge is commenced, thereby permitting the gap to quench and capacitor 630' to recharge.

As can be seen from FIG. 12A, the high-voltage capacitor 630' generates a discharge voltage pulse P.sub.1 of relatively short duration to break down the gap and initiate the discharge of a capacitor 630" of the intermediate level power supply. This capacitor 630" is connected in circuit with a charge-voltage source 631' of, say, 500 volts DC and a charging resistor 632". A diode 633" in the discharge circuit of capacitor 630" blocks opposite-polarity surges through the source 631". Discharge of capacitor 630" superimposes a pulse P.sub.2 upon the pulse of capacitor 630' and brings the gap to the point at which discharge of the low-voltage high current capacitor 630 discharges through the locking diode 633. The low-voltage supply also includes a battery 631 in series with the charging resistor 632. The long duration of pulse P.sub.3 illustrated in FIG. 12A represents the total period t of the electric discharge sustained between the electrodes and is of course determined by the capacity of condenser 630. By using a high-voltage supply to break down the gap and initiate explosive disintegration of the fusible electrode, it is possible to reduce power consumption and facilitate adjustment of the waveform.

A similar current is shown in FIG. 13 wherein, however, the main discharge current is supplied from a low-current source and is not pulsed in the fashion of the circuit of FIG. 12. In this arrangement, the electrode 724 and 727 which are partly bridged by the fusible wire 723 from supply reel 722 are energized by a gap-defining high-voltage power supply consisting of a high-voltage capacitor 730' of low capacitance which is charged through a resistor 732' by the high-voltage source 731' in series with a switch 734'.

In addition, the electrodes may be supplied by a low-voltage high-amperage power supply including a stepdown transformer 731a in series with a rectifier 731b. The input of the transformer may include the line terminals 731c and a choke 733 in series with the primary winding of the transformer and with a switch 734 which may be triggered automatically upon breakdown of the gap by the potential developed across capacitor 730' to maintain the low-voltage, high-current discharge until switch 734 is reopened or one of the electrodes 724, 727 is withdrawn to spread the gap to the point to which discharge can no longer be sustained.

In place of the low-voltage, high-current system of FIG. 13, the autotransformer arrangement of FIG. 13A may be used. In this case the autotransformer 831a is energized by a low line voltage of, say, 30 volts at 831c while the output of, say, 200 volts DC is delivered at the terminals 831d to the electrodes 727 and 724. A rectifier diode 831b is connected in series with the output of this network while a resonant circuit may be provided with the primary turns by a capacitor and an inductance as shown at 833. The network of FIG. 13A may also be used between the secondary winding of the transformer of FIG. 13 and the electrodes 724 and 727.

A modified circuit is shown for the device of FIG. 14 in which again the electrode 924 lies in the path of the fusible conductor 923 directed by a supply reel 922 and a movable electrode 927 is provided alongside the path of the fusible conductor. In this case, the high-voltage DC source for firing the gap comprises a high-voltage battery 931' in series with a current-limiting resistor 931a' and a switch 930a' which is opened once breakdown has occurred and the discharge is sustained by the low-voltage power supply. The low-voltage, high-current source comprises the battery 931 in series with a charging resistor 932 and a charging switch 934. The charging circuit is applied in parallel to a bank of high-capacitance condensers 930 which are connected in parallel with one another and in series with a rectifier 933 to the gap.

EXAMPLE

Using a copper plate as the workpiece, the plate having a thickness of 3.2 mm., a width of 200 mm. and a length of 400 mm., it was possible to shape the plate with 20 repeated discharges with a single power supply circuit of the tape shown in FIG. 2 when the capacitor had a capacitance of 3,100 .mu.F and a charging potential of 8,000 volts with kerosene as the liquid. Each discharge was the equivalent of about 100,000 joules. Using a five-section power supply analogous to that of FIG. 12 but with five capacitors and five capacitor-charging stages with capacitances of 5, 10, 300, 1,000 and 2,500 .mu.F and voltages of 1,000, 2,000, 10,000, 500 and 50 volts, respectively, each firing involved only 15,150 joules and forming was accomplished with the 20 discharges as stated.

It has already been pointed out that the thin consumable conductor or fusible electrode of the present invention may have substantially any configuration ranging from the circular cross section rod to a flattened strip. It may be noted, however, that a strip or band configuration is preferred and that it is possible to improve the rigidity of the fusible conductor as it extends across the gap by imparting a transverse curvature to the conductor as represented in FIGS. 16B and 18.

In the arrangement shown in FIG. 15, the fusible conductor 1023 is fed through a sleeve 1017j in one wall of the housing 1017 from the supply reel 1022 by a motor 1025 which drives the feed rolls 1022b. To adjust the gap G' between the fusible wire 1023 and the fixed opposing electrode 1024 in insulating sleeve 1017d, there is provided a further motor 1024a which is connected by a rack-and-pinion arrangement 1024b with the sleeve 1017j. The laterally offset electrode 1027 may also be shiftable as described in connection with FIG. 2.

While any suitable circuit may be used to apply the discharge current across the electrodes 1024 and 1027, e.g., as set forth in connection with FIGS. 12-14, the circuit may simply include a capacitor 1030 which is charged by the DC source 1031 through the resistor 1032 while discharge is accomplished via the switch 1030a whose function has previously been described. At the inlet side of the sleeve 1017j, the passage 1017j' has a rectangular and flat configuration (FIG. 16A) while at its outlet side the sleeve has a transverse curvature which it imparts to the steel band 1023, the latter being relatively long, e.g. about 100 mm., and nevertheless of sufficient stiffness as a result of the curvature to linearly span the gap. The sleeve 1017 is received within bearings 1017j" of an electrically insulating bushing 1017j'" in the wall of the housing 1017.

In FIGS. 17 and 18, there is shown a modification of the basic system of FIG. 15 in which the flat band is fed from a supply reel 1122 by the rolls 1122b driven by the motor 1125 between the roller bearings 1117j' of an insulating sleeve 1117j received in the wall of housing 1117 while the desired curvature is imparted to the band by a pair of contoured rollers 1150 and 1151 within the chamber. A ledge 1152 is formed alongside the band 1123 opposite the electrode 1127 to further deflect the band during incipient discharge.

Claims

I claim:

1. In a method of forming a workpiece by generating a shock wave which is propagated against said workpiece by electrical discharge in a liquid medium, the improvement which comprises the steps of:

temporarily bridging at least part of a gap between spaced-apart electrodes in said liquid medium with a fusible conductor by feeding a length of the fusible conductor to the gap from a location offset from the electrodes;

applying an electrical pulse across said electrodes of an intensity and for a duration sufficient to disintegrate the length of fusible conductor in said gap and produce an electrical discharge across said electrodes;

displacing said liquid medium independently of said discharge in a power jet trained against said workpiece; and

controlling a parameter of said power jet by directing selectively and generally transversely to the power jet at least one control jet of a fluid.

2. The improvement defined in claim 1 wherein said length of fusible conductor is fed along a predetermined path to said gap in the direction of one of said electrodes while the other of said electrodes is disposed adjacent said path and transversely thereto.

3. The improvement defined in claim 1, further comprising the step of maintaining a spacing between said fusible conductor and at least one of said electrodes upon the application of said electrical pulse thereby causing an incipient discharge between the conductor and the electrode spaced therefrom prior to disintegration of said fusible conductor.

4. The improvement defined in claim 1, further comprising the step of initiating the application of said electrical pulse to said electrodes by relatively displacing said conductor and at least one of said electrodes to reduce the distance between them and thereby effect breakdown of said fluid medium.

5. The improvement defined in claim 1 wherein said control jet is composed of the same fluid as the power jet.

6. The improvement defined in claim 1 wherein the control jet is regulated in accordance with a predetermined program.

7. The improvement defined in claim 1, wherein said electrical pulse includes initial high-voltage, low-current breakdown component followed by a low-voltage, high-current component sustaining the discharge.

8. The improvement defined in claim 1, wherein said fusible conductor is fed to said gap as a continuous strip, further comprising the step of stiffening said length of said conductor by imparting a transverse curvature thereto at least across said gap.

9. The improvement defined in claim 1 wherein successive lengths of said fusible conductor are successively propelled into said gap.

10. In a method of forming a workpiece by training thereagainst a power jet of a liquid and superimposing upon said power jet a shock wave produced by electrical discharge in the liquid, the improvement which comprises controlling at least one parameter of said power jet by directing generally transversely thereto a control jet of a fluid at a pressure less than that of said power jet.

11. The improvement defined in claim 10 wherein a plurality of control jets are trained at said power jet and are disposed in spaced relationship therearound, the method further comprising the step of selectively operating said control jets in accordance with a predetermined program established in dependence upon the desired forming of a workpiece.

12. In an apparatus for forming a workpiece by deformation or kinetically depositing particles thereon by generating a shock wave which is propagated against said workpiece by electrical discharge in a fluid medium in force-transmitting relationship with said workpiece, the improvement which comprises:

a shock-wave generator including a pair of spaced-apart relatively permanent electrodes;

means for feeding a length of fusible conductor to a gap between said electrodes from a location offset therefrom;

means for applying an electrical pulse across said electrodes to disintegrate the length of fusible conductor in said gap and produce an electrical discharge thereacross, said apparatus being a device for the hydroimpact forming of said workpiece and including a housing having a mouth trained at said workpiece but spaced therefrom;

means for passing a liquid at high velocity through said mouth to form a power jet of said liquid impinging upon said workpiece and upon which said shock wave is imposed; and

at least one control chamber ahead of said electrodes and formed with at least one nozzle trained transversely to said power jet for directing thereagainst a fluid control jet to regulate a parameter of said power jet.

13. The improvement defined in claim 12, further comprising guide means for directing said fusible conductor along a substantially linear path toward one of said electrodes, the other of said electrodes being disposed alongside said path and generally transversely thereto.

14. In an apparatus for forming a workpiece by deformation or kinetically depositing particles thereon by generating a shock wave which is propagated against said workpiece by electrical discharge in a fluid medium in force-transmitting relationship with said workpiece, the improvement which comprises:

a shock-wave generator including a pair of spaced-apart relatively permanent electrodes;

means for feeding a length of fusible conductor to a gap between said electrodes from a location offset therefrom;

means for applying an electrical pulse across said electrodes to disintegrate the length of fusible conductor in said gap and produce an electrical discharge thereacross;

guide means for directing said fusible conductor along a substantially linear path toward one of said electrodes, the other of said electrodes being disposed alongside said path and generally transversely thereto, the means for feeding said fusible conductor to said gap including a magazine for successively disposing individual length of said conductor in alignment with said guide means; and

means for propelling said lengths in succession to said guide means.

15. The improvement defined in claim 12 wherein the means for feeding said length of fusible conductor to said gap includes a supply of a continuous fusible conductor and feed means for dispensing the conductor through said guide means.

16. The improvement defined in claim 14, further comprising means independent of said feeding means for relatively displacing at least one of said electrodes and said conductor to establish a predetermined spacing therebetween.

17. The improvement defined in claim 14 wherein said apparatus is a device for the hydroimpact forming of said workpiece and includes a housing having a mouth trained at said workpiece but spaced therefrom, said apparatus further comprising means for passing a liquid at high velocity through said mouth to form a power jet of said liquid impinging upon said workpiece and upon which said shock wave is imposed.

18. The improvement defined in claim 12, wherein a plurality of such nozzles is provided in spaced-apart relationship around said power jet, further comprising programming means connected to said nozzles for selectively operating same with selected control jet intensities.

19. The improvement defined in claim 18 wherein at least some of said nozzles are oriented at right angles to said power jet and at least one further nozzle is oriented at an angle to the axis of said power jet.

20. The improvement defined in claim 12 wherein said means for applying said electrical pulse across said electrodes includes a high-voltage low-current source connectable across said electrodes to initiate a discharge through said fusible conductor and at least one low-voltage, high-current source connectable across said electrodes for sustaining said discharge upon its formation by said high-voltage, low-current source.

21. In an apparatus for the hydrocompact forming of a workpiece by training a power jet against said workpiece through a barrel and applying to said power jet a shock wave by electrical discharge in the liquid, the improvement which comprises means along said barrel for controlling the parameters of said power jet and including a control-nozzle trained transversely to and against said power jet and means for supplying a control fluid to said nozzle.

22. The improvement defined in claim 21, wherein the last-mentioned means includes a programmer for regulating said power jet in accordance with a predetermined series of instructions determined by the configuration to be imparted to said workpiece.

23. The improvement defined in claim 21 wherein a plurality of such nozzles are spaced around said power jet.

24. The improvement defined in claim 21, further comprising a control body ahead of said power jet for defining the cross section thereof.

25. An apparatus for forming a workpiece by deformation thereof or kinetic deposition of material thereon with a shock wave generated by a discharge in a fluid medium and transmitted by said medium to the workpiece, said apparatus comprising:

a first electrode;

guide means for feeding a length of a fusible conductor toward said electrode along a feed path;

means for passing an electrical current pulse through said length of said fusible conductor, thereby destroying said length explosively and generating the discharge in said fluid medium; and

a further electrode disposed along said path adjacent said conductor and spaced from said guide means and said first electrode, said means for passing said electrical current pulse through said length of fusible conductor being connected across said electrodes to develop a discharge therebetween upon explosive destruction of said length of fusible conductor.

26. The apparatus defined in claim 25, further comprising a magazine containing a quantity of individual length of said fusible conductor and aligned with said guide means for successively dispensing the individual length and feeding same along said path.

27. The apparatus defined in claim 25, further comprising supply means carrying a continuous fusible conductor and aligned with said guide means while being intermittently drivable for feeding successive portions of said fusible conductor along said path.

28. The apparatus defined in claim 25 wherein said fusible conductor is in the form of a strip, further comprising means for stiffening the length of said fusible conductor as it is fed from said guide means toward said first electrode by imparting a transverse curvature to said strip.

29. The apparatus defined in claim 25, further comprising a housing receiving said electrodes, said fluid medium and said fusible conductor, said housing being formed with a mouth trained in the direction of said workpiece but spaced therefrom for propelling said fluid medium against said workpiece.

30. The apparatus defined in claim 25 wherein said fluid medium is a liquid, further comprising means for displacing said liquid independently of said discharge in a power jet trained at said workpiece.

31. A method of deforming a workpiece or kinetically depositing material thereon by applying to said workpiece a shock wave generated by electrical discharge between a pair of electrodes spaced apart in a dielectric medium, said method comprising the steps of feeding a length of a fusible conductor along a predetermined path toward one of said electrodes, the other of said electrodes being displaceable toward and away from said path; connecting a source of stored electrical energy across said electrodes; and relatively displacing said fusible conductor and at least one of the electrodes to reduce the gap between them and effect a dielectric breakdown in said fluid medium to generate a discharge and explosive destruction of said length of fusible conductor.

32. The method defined in claim 31 wherein said one of said electrodes is positioned at a fixed distance from a point of intersection of an imaginary extension of said other electrode and said path, and said conductor is fed toward said first electrode, said other electrode being displaced toward said conductor to reduce the gap and cause dielectric breakdown of said medium.

33. The method defined in claim 32 wherein said fusible conductor is fed into contact with said first electrode and thereafter said other electrode is moved toward said conductor to initiate dielectric breakdown of said fluid medium.

34. The method defined in claim 32 wherein said fusible conductor is first fed along said path until it reaches a position at a predetermined distance from said first electrode and thereafter said other electrode is advanced transversely to said path toward said conductor to a position at which dielectric breakdown of said fluid medium occurs in the fluid medium across the gaps between said conductor and said electrodes to effect explosive disintegration of said conductor and thereafter form said electrical discharge directed between said electrodes.

35. The method defined in claim 32 wherein said fusible conductor is fed toward said first electrode along said path through a fixed distance and thereafter said other electrode is advanced transversely toward said conductor to a point at which dielectric breakdowns occur in said fluid medium between said conductor and said electrodes to impulsively destroying the conductor and thereafter form a direct discharge between said electrodes.

36. The method defined in claim 32 wherein said other electrode is brought into contact with said fusible conductor and said fusible conductor is then advanced along said path toward said first electrode until dielectric breakdown occurs in the gap between said conductor and said first electrode to explosively destroying said conductor and then form a direct discharge between said electrodes.

37. The method defined in claim 32 wherein said other electrode is fed to a predetermined point adjacent said path and defines a gap with said fusible conductor, and said fusible conductor is then advanced along said path to reduce the gap between itself and said first electrode to a point at which dielectric breakdown occurs across both gaps to explosively destroying said conductor and thereafter form a direct electrical discharge between said electrodes.

38. An apparatus for forming a workpiece by deformation thereof or kinetic deposition of material thereon with a shock wave generated by a discharge in a fluid medium and transmitted by said medium to the workpiece, said apparatus comprising:

a first electrode;

means for directing an electrically destructible conductor in the region of said electrode along a feed path;

means for passing an electrical-current pulse through said electrically destructible conductor, thereby destroying said conductor explosively and generating the discharge in said fluid medium; and

a further electrode disposed along said path adjacent said conductor and spaced from said means for directing said conductor along said path and said first electrode, said means for passing said electrical current pulse through said conductor being connected across said electrodes to develop a discharge therebetween upon explosive destruction of said conductor.

39. A method of deforming a workpiece or kinetically depositing material thereon by applying to said workpiece a shock wave generated by electrical discharge between a pair of electrodes spaced apart in a dielectric medium, said method comprising the steps of feeding an electrically destructible conductor along a predetermined path toward one of said electrodes, the other of said electrodes being displaceable toward and away from said path; connecting a source of stored electrical energy across said electrodes; and relatively displacing said electrically destructible conductor and at least one of the electrodes to reduce the gap between them and effect a dielectric breakdown in said fluid medium to generate a discharge and explosive destruction of said conductor.

40. In a method of hydroimpact forming a workpiece by directing a power jet of a liquid in shock-transmitting relationship therewith, the improvement which comprises controlling at least one parameter of said power jet by directing generally transversely thereto a control jet of a fluid at a pressure less than that of said power jet.

41. The improvement defined in claim 40 wherein said power jet of liquid directed by generating an impulsive electrical discharge in said liquid.

42. In an apparatus for the hydroimpact forming of a workpiece by directing a power jet of a liquid in shock-transmitting relationship therewith through a barrel, the improvement which comprises means along the path of said power jet for controlling at least one parameter of said power jet and including a control nozzle trained transversely to and against said power jet and means for supplying a control fluid to said nozzle.

43. The improvement defined in claim 42 wherein said power jet is directed by generating an impulsive electric discharge in said liquid within said barrel.

44. In a method of hydroimpact forming a workpiece into an intricate shape having a plurality of recesses by sweeping masses of a high-velocity liquid power jet in shock-transmitting relationship over said workpiece, the improvement which comprises controlling a parameter of said masses in accordance with the configurations of said recesses.

45. The improvement defined in claim 44 wherein said parameter is at least one of the velocity and the configuration of said mass.

46. An apparatus for hydroimpact forming of a workpiece into an intricate shape, comprising a die having a plurality of recesses; means for projecting a high-velocity power jet in shock-transmitting relationship against a workpiece juxtaposed with said die so that said jet sweeps across said recesses to deform said workpiece into same; and means for controlling a parameter of said power jet in accordance with the configurations of said recesses.

47. The apparatus defined in claim 46 wherein the last-mentioned means is so constructed and arranged as to control the velocity of said power jet.

48. The apparatus defined in claim 46 wherein the last-mentioned means is so constructed and arranged as to control the configuration of said power jet.

49. A method defined in claim 31 wherein said discharge is generated by an electrical pulse including an initial high-voltage, low-current breakdown component followed by a low-voltage, high-current component sustaining the discharge.