US3498904A - Electrode for electrolytic shaping - Google Patents

Description

75inch 5 1 L. A.WILLI I'\MY S ELECTRODE FOR ELECTROLYTIC SHAPING 1 2 Sheets-Sheet 1 Original Filed Nov. 10, 1958 3,498,904 ELECTRODE FOR ELECTROLYTIC SHAPING Lynn A. Williams, Winnetka, Ill., assignor to Anocut Engineering Company, Chicago, 10., a corporationof 1015 Application Feb. 14, 1966, Ser. No. 552,652, now Patent No. 3,421,997, which is a continuation of application Ser. No. 165,569, Jan. 11, 1962, which in turn is a division of application Ser. No. 772,960, Nov. 10, 1958, now Patent No. 3,058,895, dated Oct. 16, 1962. Divided and this application Jan. 2, 1969, Ser. No. 788,482

Int. Cl. B23p 1/02; B01k 3/04 US. Cl. 204-284 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCES TO RELATED PATENTS This application is a division of my application Ser. No. 552,652, filed Feb. 14, 1966, now Patent No. 3,421,- 997, which application is a continuation of my applica tion Ser. No. 165,569, filed Jan. 11, 1962, now abandoned, which application is a division of my application Ser. No. 772,960, filed Nov. 10, 1958, entitled Electrolytic Shaping now issued into Patent No. 3,058,895, dated Oct. 16, 1962.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to electrodes for use in electrochemically shaping metal and metalloid materials.

Description of the prior art It has long been known that metal and metalloid materials may be removed by electrolytic attack in a configuration where the metal or metalloid workpiece is the anode in an electrolytic cell. This principle has been used industrially to some degree for the removal of defective plating and the like, and is sometimes referred to as stripping. It has also been used to some extent for electrolytic polishing, in which application, however, the principal purpose is to produce a smooth finish with a minimum removal of the work material. Here the purpose is to remove substantial amounts of metal rapidly and with accuracy.

SUMMARY OF THE INVENTION In the present instance, the term metalloid is used somewhat specially in referring to those electrically conductive materials which act like metals when connected as a anode in an electrolytic cell and are capable of being electrochemically eroded. The term as used here and in the claims includes metals and such similarly acting materials as tungsten carbide, for instance, and distinguishes from such conductive non-metalloids as carbon.

George F. Keeleric has proposed in his Patent No. 2,826,540, issued Mar. 11, 1958, for Method and Apparatus for Electrolytic Cutting, Shaping and Grinding the use of electrolysis in conjunction with a metal bonded, abrasive bearing, moving electrode, and the method and United States Patent O 3,498,904 Patented Mar. 3, 1970 apparatus of this Keeleric patent have found extensive industrial use.

The present invention departs from the teachings of Keeleric in utilizing relatively fixed or slow moving electrodes without abrasive, and is intended for work of a quite different character, as will appear in the detailed description of the invention which follows:

In general, in the present invention an electrode, quite frequently a hollow electrode, is advanced into the work material by mechanical means while electrolyte is pumped through the work gap between the electrode and the work, and at times the hollow portion of the electrode, under substantial pressure. In some circumstances, the side walls of the electrode are protected by an insulating material so as to minimize removal of work material except where desired. Various forms of electrodes are used for different kinds of Work, and likewise different techniques advancing the electrode toward and into the work material are used, depending upon the nature of the operation to be performed. In the present application porous metallic electrodes are the subject of the invention.

An important aspect of the invention lies in providing electrodes in which a flow of electrolyte between the electrode and the work is maintained at high velocity and across a short path between the point of entry and the area of exit regardless of the over-all size of the electrode. An electric current is supplied so that current passes from the electrode, which is negative, through the electrolyte to the workpiece, which is positive. For purposes of shaping the electrodes, direct current may be passed in the opposite sense to make the electrode positive. In some instances, alternating current may be used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one form of apparatus utilizing the electrode of the present invention;

FIG. 2 is a diagrammatic representation of an electro lyte supply system which forms a portion of the apparatus of FIG. 1;

FIG. 3 is a longitudinal sectional view through an electrical tip which makes use of a porous metal element at the working face thereof;

FIG. 4 is a perspective View of the working end of another electrode in which the working tip is formed of a porous metal and particularly adapted for sinking cavities or comparatively large areas; and

FIG. 5 is a transverse sectional view taken along the line 55 of FIG. 4 looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the apparatus includes a frame member 1 which in this instance is the frame member of a conventional and well known arbor press sold under the trade name of FAMCO. It includes a base section 3, a column 5, and a head 7 which is adapted in the conventional manner to accommodate a ram 9 for vertical reciprocating motion. The detail of the ram mounting is not important to this invention, but it is desirable to provide adjustable gibs or the equivalent in the head so that the ram may move vertically with a smooth action and without lateral play which might introduce undesired side motion. To the bottom end of the ram 9 there is mounted a workplate 11 through which a plurality of bolt holes is provided to permit adjustable mounting of a work-holding vise 15.

On the base portion 3 there is mounted a metal bottom plate and on top of this a waterproof, chemicalresistant plastic mounting plate 19. This is provided with a number of threaded bolt holes to permit mounting of an electrode holder 21, which is made of suitable metal and is provided with one or more mounting slots so that 3 r it can be adjusted as to its position by'selection of the suitable bolt holes in mounting plate 19.

At the working end, the electrode support member 21 is hollow and is adapted to receive an electrolyte feed tube fitting 27 connected to a line leading to a source of electrolyte under pressure.

Extending from the upper surface, there is mounted on electrode 31, shown here as fastened by brazing to a pipe nipple threaded into the electrode support member 21. Within the hollow support member 21 the electrode is connected by a suitable passage to the feed tube fitting 27.

An electric cable is connected to the electrode block or support member 21 and supplies current from the power source. Another electric cable 35 is fastened to work plate 11 to furnish the other (normally positive) connection from the power source.

To move the work plate 11 up and down, a lead screw 37 is secured to and extends upwardly from the upper end of the ram 9. A lead nut 39 is threaded upon the lead screw and is mounted between two horizontal plates 41 which are supported by four column bars 43. The lead nut peripherally is formed as a worm gear so that it may be rotated to move the lead screw 37 up and down. A journal plate 45 is mounted to the plates 41 and carries a bearing bushing 47 which supports the outboard end of a drive shaft 49 which carries worm 51 meshed with the peripheral worm gear of lead nut 39.

The worm drive shaft 49 is in turn rotated by 21 variable speed electric motor drive 53 mounted upon a platform 55 attached to the column 5. This drive mechanism has a speed adjusting handle 57 and a reversing handle 59, the latter having a neutral mid-position as well as updrive and downdrive positions.

The sizes and proportions of the drive parts are arranged to permit adjustment in the vertical speed of movement of the work plate 11 from zero to one inch per minute. The motion must be smooth, not jerky, and accordingly, reasonable accuracy and freedom from excessive friction are an advantage in the moving drive parts. The lead screw 37 may be protected against splatter and corrosion by a plastic enclosure 61 wrapped around the column bars 43.

A conventional dial indicator 63 is shown as mounted to the head 7 of column and has its working tip extended downwardly against the upper surface of work plate 11 so as to indicate relative movement as between these elements.

The entire assembly is mounted in a pan 65 which has an outlet spud adapted to drain electrolyte back into a supply sump or reservoir 74. The work plate 11 is fitted with plastic curtains 71 which can be tucked down below the level of the pan top to prevent excessive splatter.

The plumbing system (FIG. 2) comprises a low pressure pump 73 which feeds electrolyte from the reservoir 74 through a filter 75 into high pressure pump 77, the outlet of which leads to a bypass valve 79 which may be either manually set or of the spring loaded constant pressure type. On the inlet side of the bypass valve 79 a pressure gauge 81 is mounted. Also from the inlet side, a pipe .lead is taken through a needle valve 83 to an electrolyte feed tube 84 leading to the electrode fitting 27. A secondtgauge 29 is connected to the feed tube 84 so as to indicate the pressure at the electrode.

, In operation, a workpiece is positioned in the vise 15 above the electrode 31, and the work plate 11 is then driven down until the workpiece is almost touching electrode 31 as gauged by a piece of paper or shim of known thickness, say .003 inch. The dial indicator 63 is then adjusted to zero minus the known thickness, .003 inch in this example. The curtains-'71 are lowered ,or otherwise closed, the electrolyte pumps 73 and 77 are started, and the valves 79 and 83 are adjusted so that gauge 81 reads about 120 p.s.i. and gauge 29 about 90 p.s.i. This is .done while thereversing handle 59 is in neutral positionThen,

simultaneously, the reversing handle is moved to downdrive position, and the electric power supply is turned on.

As the electrode approaches the workpiece, there will be a rise in pressure at the gauge 29. If the capacity of pumps 73 and 77 is several times the free flow discharge rate through the electrode, the pressure upstream of the needle valve 83 and of bypass valve 79 as read at gauge 81 will change scarcely at all wtih changes in proximity of the electrode 31 to the work, for most of the flow is passing through bypass valve 79, and it is the adustment of this which is principally determinative of the pressure at gauge 81. In short, the pumps and plumbing system up to needle valve 83 constitute a substantially constant pressure source. The same result may be obtained in many other ways. A constant pressure type pump may be used, e.g., a centrifugal pump operating near cutoff. Or a pressure regulator may be used. Or a spring loaded relief valve adapted to maintain constant pressure maybe used.

Needle "valve 83, however, is set so as to constitute a sufiicient restriction to flow'so that when the electrod is discharging into the open, the pressure as read at gauge 29, will be noticeably lower than when its outlet is restricted by being in. close proximity to the work.

Thus, if gauge 81 normally reads 120 p.s.i., then when the electrode 31 touches the workpiece so as to shut off the flow, or nearly so, the pressure downstream of needle valve 83 as read at gauge 29 will rise to almost the same value, 120 p.s.i. If, however, the electrode 31 is spaced away by several thousandths of an inch, the pressure at gauge 29 will drop, say to 90 p.s.i.

This change in liquid pressure may be used in adjusting the rate of feed of ,the work toward the electrode. The initial feed rate may be set at a low level (for an unknown working condition or work material) and then increased by adjustment of the handle 57. Gauge 29 is observed to watch for a pressure rise which approaches that of gauge 81. It takes a little time for the pressure reading to stabilize during actual removal operations, for inasmuch as material is being removed by anodic dissolution, it is necessary for the moving electrode to catch up with the receding work material and to establish an equilibrium spacing distance, for as the electrode comes closer to the work, the removal rate tends to increase. By the exercise of reasonable care, it is possible to make a precise adjustment such that the electrode pressure-gauge 29 reads only a few pounds per square inch lower than gauge 81, indicating that the electrode is moving forward at such a rate as to leave only a small gap between the electrode and the work.

In effect, this hydraulic system constitutes a flow meter, and. the same result-may be obtained by using a more formal flow meter to sense the flow rate through the gap between the electrode and the work. Such flow meter may be of any suitable sort, as for instance of the orifice type (which, in eflect, uses the principle of the system just described) or of some. other type, for example, that in which amoving bob is supported by upward flow in a conical glass vessel (e.g., the Fischer and Porter type).

It isnot easy to measure this gap with accuracy, as apparently it is not always uniform at every point, but as measured in a practical way, by turning off the current and advancing the electrode until it seems to bottom, the

7. distance maybe as small as .001 inch or less, to as much as .010 inch, with satisfactory results, although it is preferred to work with the shortest spacing distance which can be managed without causing occasional contact and arcing between the electrode and the work, and I have found that about .002 inch to .005 inch is usually a safe distance 'while still permitting rapid removal of work material. 7

In general, low voltages and close spacing, of the order of. .001 inch to .005 inch, 'give high removal rates and low electric power costs and a higher degree of accuracy, but less striation is produced upon the side wall of the work cavity when greater spacing, of the order of .010 inch, is used. The greater spacing results in a lower work removal rate unless the voltage is raised however, since removal rate is a function of current. As a practical matter in most applications, I prefer to use about volts and from 100 to 3000 amperes per square inch of active electrode area.

It should be noted that work material is removed by electrolytic action, not by spark or arc erosion, as with the so-called electrodischarge method. This is important for several reasons, among them the fact that damaging thermal metallurgical effects on the work material are avoided and that there is virtually no erosion of the electrode. The fact that the electrode is not eroded is of great importance where the cavity is to be accurately shaped,

for accurate shaping is rendered very difiicult when the electrode is being eaten away at a rate rapid enough to alter its dimensions during the operation.

Thus, it is important to avoid too fast a feed rate which may cause arcing between the electrode and the work.

Another method of gauging the feed rate is by reference to an ammeter in the electrolytic power supply circuit. Once the penetration of the electrode into the work has been well established, the rate of feed is gradually increased until an arc is observed. Usually this will be of short. duration. The reading of the ammeter is ob served and read just prior to the first arc, and the speed is then adjusted downwardly until the ammeter shows a reading of little below the critical point where the first arc occurred.

A transducer sensitive to either the electrolyte liquid flow rate or the electrolytic electric current may be used as the signal generating element in an automatic feed control system. 1

FIG. 3 shows in section an electrode end in which the porous metal member 321has been fastened by rolling the tube body 275 into an annular groove 322 in the porous metal element, which is also shaped to form. the working lip 281. Ceramic coating 283 is then applied to the exterior of the electrode.

This electrode is suitable for small areas, but I have found that when the diameter of a porous metal type of electrode tip is as large as 1 inch, thework is left with radially extending grooves probablycaused by liquid exitingv irregularly from the mid-area of the tip. The path from the point of introduction of electrolyte to the point where it leaves the active work area should preferably be kept short, and I prefer to keep this distance under /s inch to M4 inch. v

When it is desired. to produce cavities having a better finish, I prefer -to use electrodes constructed generally after the fashion illustrated in FIGS. 4, and 5. The electrode of FIGS. 4 and 5 is essentially similar to the one shown in FIG. 3 in that a piece of porous metal 321 is secured at the working end of a tubular electrode member 275. It is preferable, however, for use in forming cavities of larger size than the electrode illustrated in FIG.,3, since it provides for an escape of the electrolyte from the interface between the electrode tip and the work.

The porous metal member 321 is provided with one or more transverse holes 339 which are connected to the working face of the electrode by a plurality of smaller holes 341. The electrolyte, therefore, under pressure within the tube 275 finds its way to the working face of the electrode through the tortuous passages within the porous member 321, and this electrolyte then escapes by way of the small passages 341 to the larger channels 339 which carry the electrolyte away from'the work. If it is found that an excessive amount of electrolyte escapes directly into the channel 339, for instance, without reaching the work, these channels can be sealed as by burnishing, for instance, and this treatment may also be given to the smaller passages 341 so that although there may be some leakage directly into these passages, such leakage is a minor consequence. Alternatively these surfaces may be lightly tinned with solder or plated to effect the seal.

All of the electrodes discussed above may be relieved to a shallow depth at their side faces, and this recessed portion may be coated with a ceramic layer which is for the purpose of inhibiting side action as between the electrode and the side walls of the cavity. Furthermore, the end face of this and other electrodes may be shaped by deplating; that is, by reversing the current and plating away the end face of the electrode as it approaches a shaped tool which has a contour which is the negative of the contour desired upon the electrode.

The purpose of the enamel coating is to utilize its insulating properties to minimize electrolytic side action between the electrode body and the side walls of the cavity.

Vitreous enamel is the best coating I have found, but other insulating materials may be used. I have found Teflon quite satisfactory where it can be easily applied. However, the organic lacquers and paints which have been tested have not been very satisfactory because they seem .to be chemically or physically attacked near the working tip. The vitreous enamel seems to be quite impervious to such deterioration.

Copper is a good substance for forming the electrode because it is a good electrical conductor, but good success has been had with cold rolled steel. Brass may be used, but it is ditficult to get a good vitrified enamel coating on brass, and accordingly, it is not preferred. All of these materials are, in general, somewhat less satisfactory than stainless steel or titanium in that they are susceptible to the formation of plating deposits which, under some conditions, may make the outline of the electrode less clean, and in some instances such deposits may change the current fiow characteristics of the system.

From the above description of my invention which has been illustrated in several embodiments and variations, the features and applications of the inventive idea to practical problems have been discussed. From this it will be apparent that certain generalizations may be made.

The amount of metal removed from a workpiece by electrolytic action is a direct function of the current in the electrolyzing circuit. The voltage necessary to pass any particular current with any particular set of circumstances will'depend upon the spacing between the electrode and the workpiece. It will also depend upon the electrode size or effective area, but for a particular job the electrode size usually will not be a variable.

The cost of operation will vary rather directly with the wattagethat is, the amperage in the circuit times the voltage necessary to produce the current. From these con-' siderations it follows that from the practical standpoint it is'essential that the electrode to workpiece spacing be held to a practical minimum so that minimum voltages may be used, thereby enabling the operation to be conducted at minimum cost. As an example, by following the teachings of the present invention, precisely held small spacings may be used and most electrolyzing operations may be conducted at approximately ten volts or, in some cases, even less with work gaps from half a thousandth to a few thousandths of an inch. The current densities which appear to be most satisfactory as a practical matter are between and 3000 amperes per square inch of effective electrode area. The wattage, therefore, is between one and thirty kw. per square inch. For large areas the voltage may be reduced to four volts while still obtaining reasonable current density.

All prior systems with which I am familiar, which attempt to remove metal by electrolytic action, require far greater total electric energy than this to remove an equivalent amount of metal. Prior workers in this field have found it necessary to use voltages of the order of 100 to volts or more with the result that the energy requirementsor in other words, the cost of removing the 7 metal-are of the order of ten or more times that required when using the invention discussed above. Furthermore, if low voltages are attempted with wide work gaps, the rate of material removal is low and thus more machines are required to produce the same amount of work. It is apparent, therefore, that regardless of the approach to the problem, the accomplishment of high current densities with low voltages is economically essential.

Also, as previously indicated, high voltages together with comparatively large work gap spacings produce an electrolytic action that is far less controllable, and therefore the work produced cannot be as precise as the work produced by using the present invention.

Air jets may be used to prevent unwanted electrolytic action between side surfaces of the electrode and the work, where the electrode is not in close proximity to the work but where electrolyte is caught in stagnant pockets. The air is used to blast away the stagnant electrolyte. The arrangement of FIG. 1 in which the work is positioned above the electrode is also helpful in eliminating stagnant electrolyte pockets as gravity causes the electrolyte to fall away from the work area. This is the case in forming cavities in the work. Where the part to be produced is a punch or the like so that there is a cavity in the electrode, then the electrode is placed above the work so that gravity helps to clear away the electrolyte except where there is close spacing between the electrode and the work.

A wide variety of electrolytes may be used in the apparatus and processes heretofore described. Some work materials respond to acid solutions of 5% to 25% of the appropriate strong acids such as hydrochloric, nitric and sulphuric. Other materials, such as cemented carbidese.g., tungsten, tungsten carbide, titanium carbide, etc. respond better to caustic solutions such as a solution of potassium hydroxide to which may be added 5% sodium tungstate.

To the extent possible without excessive loss of removal rates, it is preferable to use neutral or nearly neutral salt solutions because they are much easier and safer for routine shop handling. A solution of this type which has shown good versatility and good removal rates may be made by adding to 15 gallons of water the following:

This solution, when supplied to, the electrode at a temperature between 120 F. and 150 R, will give good removal rates on a wide variety of steels, including stainless steel, and also a great many of the so-called superalloys of nickel, cobalt or iron base and containing as alloying materials, in addition to those three, such materials as chromium, molybdenum, tungsten, titanium, columbium, etc.

In addition to removing material at good rates, a good finish is obtained, and particularly on the high alloy stainless steels and the super-alloys, a bright, reflective surface may be created where the surface is exposed to electrolysis under conditions of pressure and high velocity in the electrolyte, as previously explained.

I have found that an essential to good performance of an electrolyte is that the metal salt products of electrolytic decomposition be readily soluble. For example, aluminium is not easily worked by this process with many electrolytes which are usable on other materials, as the anodic action forms aluminium salts which are not very soluble or not soluble at all and form an anodic film on the work. But a simple 5% or 10% solution of acetic acid yields good results because the relatively complex aluminium salts formed are soluble enough to be readily washed out of the work gap.

Where fine detail of pattern is to be reproduced, it is desirable to use a solutionwhich is considerably more dilute than is desirable for maximum removal rates. Thus, the quantities of salts used in the table above are reduced to one fourth to one sixth of the values shown for the same amount of water. The voltage applied is also reduced. The purpose is to accentuate the difference in removal rate between those areas where the electrode is close to the work and those where it is more remote. If the electrolyte is too conductive and the applied voltage is too high, then the difference in resistance path between areas of close proximity and others of greater spacing is not very great, and the detail of pattern becomes blurred. Referring tothe solution in the table, this has been used successfully in a four-to-one dilution to duplicate coin patterns in the following configuration and procedure. First, a coin is positioned oppositean electrode like that of FIG. 3, using a disc electrode of porous sintered bronze in the form of a disc about one inch in diameter and A5 inch thick. The electrolyte is pumped at about p.s.i. through the electrode disc after passing through a filter designed to remove all particles down to five microns. The electrolyzing current is first connected in a sense to make the electrode positive. The electrode is then advanced until it'very nearly touches the coin. Thencurrent is turned on at four volts for one or two seconds, the electrode is then advanced, and this is repeated until ample depth has been reached to embrace all of the'coin face pattern. Then the coin is removed and replaced with a piece of die steel, and the power leads are reversed so that the electrode is now a cathode. The electrode is now advanced toward the steel, using a voltage of six volts, and again, very close proximity is used --a few ten-thousandths of an inch of spacingand the electrode is advanced into the steel to a depth great enough to embrace the pattern. By this means, it has been possible to reproduce fairly fine detail, and in comparing the height of the coin pattern above its fiat areas with the finished steel replica, it has been possible to bring these measurementswithin less than .001 inch of difference between the original coin and the steel pattern. So far as I am aware, such close copying by electrolytic removal'means has never been approached before.

.In the foregoingv description, various parameters have been described with respect to the apparatus components and the steps which are embodied in the method of carrying outthe present invention. In the following claims it is intended that, the language used in describing the apparatus components and the method steps be related within the range of permissible and reasonable equivalency to the description and disclosure. For example, it has been found that reasonably good results can be obtained by furnishing the electrolyzing direct current within the range of approximately four to 15 volts. Within this approximaterange, and depending upon the resistance in the. work'gap, the'current density will usually be in the range of 100 to 300( or more amperes per square inch. The resistance in the work gap is determined by the width of the gap and'the character of the electrolyte therein. Work gaps'ofless than .001 inch, e.g., .0005 inch, and as great as, ,012 inch: havebeen described. When the electrolyte 'ispumped through such gaps at temperatures in the range of- F. to F., a pressure of several atmospheres. mustlbe-used to inhibit bubbling or boiling of the electrolyteand the consequent reduction of its conductivity. Therefore, the electrolyte is pumped through the gap atpressureswithin the range of 50 p.s.i. to at least 200 p.s.i. to obtain high back pressure in the work gap with a resultant high electrolyte velocity through the work gap, thereby. substantially to raise the boiling point level of the electrolyte so as to inhibit the formation of gas bubblesin the electrolyte and to flush away the eroded workpiece material. p I From the above discussion it'will be apparent that although this invention may be used for producing shapes and cavities of an irregular character, such that they would be extremely difficult to form by any other process, the invention also has a high order of utility for replacing more conventional machining operations when the workpiece is one of the super-alloys or other material which is for all practical purposes, largely non-machinable.

From the above description of my invention as embodied in several alternative variations, it will be appreciated that many changes may be made both in the apparatus and in the method without departing from the scope or spirit of the invention, and that the scope of the invention is to be determined from the scope of the accompanying claims.

I claim 1' 1. An electrode for use in electrolytic shaping apparatus, comprising a hollow metallic member adapted to be connected into an electrolyzing electric circuit, said member having a working and electrically conductive tip at one end thereof adapted to be brought into close spacing relationship with a metallic workpiece to be shaped, said member having an opening opposite said Working tip through which an electrolyzing fluid is adapted to be pumped, said member having a minor metallic area contiguous to said tip and exposed laterally to provide controlled lateral electrolytic erosion of the workpiece, said member being formed of a porous metallic material, and an insulating sheath encasing and secured to said tubular member from said laterally exposed area toward and substantially to said end of said member opposite said Working tip.

2. The electrode claimed in claim 1 wherein said member of" porous metallic material is formed of sintered metal.

3. The electrode claimed in claim 1 wherein said tip has a laterally projecting lip to provide controlled lateral electrolytic erosion of the workpiece.

4. The electrode claimed in claim 1 wherein said memher is tubular.

5. An electrode for use in electrolytic shaping apparatus, comprising a hollow metallic member adapted to be connected into an electrolyzing electric circuit, said member having a working and electrically conductive tip at one end thereof adapted to be brought into close spacing relationship with a metallic workpiece to be shaped, said member having an opening opposite said working tip through which an electrolyzing fluid is adapted to be pumped, said member being formed of a porous metallic material.

6. The electrode claimed in claim 5 wherein said porous metallic material has passages formed therein.

7. The electrode claimed in claim 5 wherein said member has a minor metallic area contiguous to said tip and exposed laterally to provide controlled lateral electrolytic erosion of the workpiece.

8. The electrode claimed in claim 7 wherein an insulating sheath encases and is secured to the tubular member from said laterally exposed area toward and substantially to said end of said member opposite said working tip.

9. The electrode claimed in claim 5 wherein said working tip is provided with passages therethrough and with connecting conduits to said passages for permitting removal of electrolyte from the Work.

10. The electrode claimed in claim 9 wherein said member is hollow for introducing said electrolyte to said porous tip for passage therethrough.

References Cited UNITED STATES PATENTS 2,539,455 1/1951 Mazia 204140.5

JOHN H. MACK, Primary Examiner D. R. JORDAN, Assistant Examiner US. Cl. X.R. 204224 Dedication 3,498,904.Lynn A. Williams, Winnetka, I11. ELECTRODE FOR ELEC- TROLYTIC SHAPING. Patent dated Mar. 3, 1970. Dedication filed Dec. 23, 1971, by the assignee, Anocut Engineering Company. Hereby dedicates to the Public the portion of the term of the patent subsquent to Dec. 24 1971.

[Ofiiciai Gazette Ayn-i118, 1.972.

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