US2848410A - Apparatus for the electrolytic polishing of limited surface portions of a metallic workpiece - Google Patents

Description

Aug. 19, 1958 2,848,410

. E. C. F. KNUTH-WINTERFELDT ETAL APPARATUSES FOR THE ELECTROLYTIC POLISHING 0F LIMITED SURFACE PORTIONS OF A METALLIC WORKPIECE Filed April 30, 1956 2 Sheets-Sheet l INVENTORJ Eeczwr C. F. Kmma -Wnmzm=sun Lnumrz G, Dame R1? MM M rm ATTORNEYS Aug. 19, 1958 2,848,410

E. C. F. KNUTH-WINTERFELDT ETAL APPARATUSES FOR THE ELECTROLYTIC POLISHING OF LIMITED SURFACE PORTIONS-OF A METALLIC WORKPIECE Filed April 30, 1956 2 Sheets-Sheet 2 Fig.

INVENTORS EGGERT CHI-T KNUI'H VmTERFeLm LAURITZ C DANG/MRI) BY m, M, M 9 #2123,

ATTORNEYS United States Patent Ofiice 2,848,410 Patented Aug. 19, 1958 APPARATUSES FOR THE ELECTROLYTIC POLISH- ING OF LIMITED SURFACE PORTIONS OF A METALLIC WORKPIECE Eggert Christian Flemming Knuth-Winterfeldt, Gentofte, and Lauritz Gndmund Damgaard, Virum, Denmark, assignors to H. Struers Chemiske Laboratorium, Copenhagen, Denmark This invention relates to an apparatus for the electrolytic polishing of limited surface portions of a metallic workpiece for the purpose of subjecting the polished area to a structure test. This method is used to an increasing extent for the testing of materials and construction parts.

The principle of electrolytic polishing is that the surface area to be polished is brought into contact with an electrolyte, whereafter a potential difference is created between the workpiece and an electrode in the electrolyte. Moreover, to obtain a uniform polishing it is important that during the electrolytic process there should be a certain flow motion of the electrolyte relative to the surface area to be polished.

To fulfill these conditions, apparatuses have been used for electrolytic polishing, having a mouthpiece to be applied in contact with the workpiece, and means for conducting an electrolyte to and from the mouthpiece as well as means for creating a potential difference between the electrolyte and the workpiece.

In some known apparatuses of this type, the mouthpiece is mounted on a stationary equipment comprising a tank and circulation pump for the electrolyte as well as electrical equipment for creating the potential difference. In apparatuses of this type, it is possible to construct the mouthpiece and the circulation path of the electrolyte in such a manner that a relatively great area can be swept in a satisfactory manner with a flowing electrolyte, so that a uniformly polished spot of -relatively great size can be obtained. However, these apparatuses have the drawback that only relatively small workpieces can be polished, because these must be clamped to the mouthpiece. This again means that the apparatuses inquestion are only suitable for the testing of samples of material, e. g. cut out of construction parts in a running production, but ordinarily not for the so called intact testing of the workpieces themselves.

On the other hand, it has been proposed for intact testing purposes to use a mouthpiece in the form of a pipette, which is applied to the work piece at the spot where the latter is to be polished, and to which an electrolyte is supplied through a flexible tube and is thereafter permitted to flow ofi freely from the point of contact between the workpiece and the pipette, the mouth of which may be specially constructed for the purpose of obtaining auniform and controlled flow off. With this apparatus, a great flexibility of application and full possibility of intact testing are obtained, but on the other hand, it is only possible to produce a very small polished spot, which is far too limited for certain examinations.

The present invention relates to an apparatus of the same type as above described, and it is the object ofthe invention to construct an apparatus of this type in such a manner as to obtain the same flexibility of application and the same possibility of intact testing as with the apparatuses last described, while still extending the polish ing to an area of the same order of size as with the apparatuses first described.

To achieve this, according to the invention, the mouthpiece is mounted on a handle, which is connected with a source of electrolyte through flexible liquid conduits and is provided with an operating member for cutting off the supply and discharge of electrolyte to and from the mouthpiece.

With an apparatus of this construction, the workpiece must not be clamped to the mouthpiece, but the latter will simply be pressed against the workpiece by means of the handle on which it is mounted. It is therefore possible to polish an existing workpiece at any place thereof without damaging the workpiece, i. e. there is full possibility of intact testing. On the other hand, there exists a two-way circulation path for the electrolyte so that it becomes possible to cause the latter to sweep a relatively great area uniformly within the circumference of the mouth piece, whereby it again becomes possible to produce a considerably greater polished area than with the pipette apparatuses. The correspondingly greater quantity of the electrolytic liquid that must be caused to flow in the mouth piece is returned through a return conduit and thus does not have to drip off from the operating position. Consequently, the waste of electrolyte and the drainage of the latter to the surroundings of the testing spot, which is characteristic of the pipette apparatuses, and which would be of great disadvantage in apparatuses for the polishing of greater areas with use of corresponding quantities of electrolyte, are avoided. It is also important that an operating member for cutting off the supply and discharge of electrolyte to and from the mouthpiece is provided on the handle itself, because it becomes thereby possible to start the circulation of the electrolyte only in the moment the mouthpiece has been correctly applied to the workpiece, even if in this moment the handle should be relatively remote from the other equipment employed.

According to the invention, the mouthpiece may advantageously be mounted on the handle by means of an articulated joint, whereby the mouthpiece will be capable more easily of applying itself sealingly to the workpiece than if it were rigidly connected with the latter. According to one method of constructing the said articulated joint, the mouthpiece is mounted on a pin which is rotatably mounted in the handle for rotation about an inclined axis intersecting the axis of the mouthpiece in a point in the vicinity of the face of the mouthpiece to be applied to the workpiece. This construction provides a simple means of obtaining a secure and stable engagement of the mouthpiece with the surface of the workpiece.

To obtain the cutting ofi of supply and discharge of electrolyte to and from the mouthpiece, the flexible liquid conduits may be in the form of flexible tubes extending from'the mouthpiece through the handle, a squeezing member operated by the said operating member being provided in the handle and serving to squeeze the flexible tubes.

With particular advantage, the squeezing means may be'arranged to perform, in the operation of squeezing the flexible tubes, a sweeping movement longitudinally of the latter in a direction away from the mouthpiece. By this means the tendency to dripping from the mouthpiece after the circulation of electrolyte therethrough has been stopped is minimized.

In order that the squeezing member should subject the flexible tubes to as little wear as possible while squeezing and sweeping along the latter, the squeezing member may preferably be in the form of a roll, which is mounted at the end of a lever mounted in the handle and forming the operating member.

For the purpose of facilitating the operation, the said lever may 'be biased by means of a spring tending to turn the lever in a direction toward "the squeezing position, the said spring being arranged in such a manner that the moment arm on which it acts becomes shorter when the lever is turned away from the squeezing position. The advantage of this is that in the resting position, in which the lever is to be kept while the electrolytic polishing is being performed, it will only be subjected to a relatively small biasing torque so that it'requires little force to hold the lever in this position, while on'the other hand in the position where the lever is to squeeze the flexible tubes it is subjected to a strong biasing'torque so as to etfect a powerful squeezing'under the influence of the spring.

The manner in which the liquid is caused to flow in the mouthpiece is very important in order to obtain the best results. It has been 'found that the principles of flow which have previously been used in apparatuses with a stationary mouthpiece are not directly suitable for'adoption in the apparatus here concerned. It has been found that an advantageous type of flow giving a uniform polishing can be obtained if the mouthpiece is constructed with two 'co-axial passages opening at a small'distance behind the face of the mouthpiece to be applied to the workpiece, the outer meat which passages is connected with the supply, while the inner passage is connected to the discharge for the electrolytic liquid. The inwardly directed flow of the electrolyte obtained in this manner has been found to be far superior to the outwardly directed flow which is frequently used in apparatuses with stationary mouthpiece and also in'the above mentioned apparatuses with pipette. To obtain the best possible results it has been found advantageous to provide guiding means imparting a circular movement to the incoming electrolytic liquid at the opening ofthe outer one of the co-axial passages.

To enable the mouthpiece to fit as closely as possible to the surface of the work piece, it is proposed according to the invention to construct the mouthpiece in such a manner that the wall of the part of 'the mouthpiece extending beyond the mouths of the co-axial passages consn'tutes an elastic sleeve.

Preferably, the arrangement should be such that the electric circuit can only be completed when the mouthpiece has been applied to the workpiece and the flow of electrolyte has been started. To obtain this, according to the invention, the operating member on the handle may be adapted, towards the end of its movement for setting free the flow of electrolyte to and from the-mouthpiece, to close a contact in the electric circuit'for estab-' lishing the required potential difference between the electrolyte and the workpiece.

As mentioned, the flexible conduits from the handle should be connected to a source of electrolyte during the use of the apparatus from which source a circulation of electrolyte through the flexible conduits and the mouthpiece should be caused.

In many cases, the laboratory or workshop using the apparatus according to the invention will already have available an apparatus of the above described type with a stationary mouthpiece, and in that case the handle with the mouthpiece and the flexible conduits may be used as an attachment to the existing apparatus, the flexible conduits being connected to the electrolyte circuit of the existing apparatus in suitable manner. The latter also supplies the necessary potentials to the work piece and to an electrode provided in the handle. However, as far as the electrolyte circuit is concerned, it is frequently advantageous to be independent of other apparatuses for producing the circulation of electrolyte, among other things in order to obtain a greater flexibility of use and independence of the pressure levelywhich an existing apparatus is capable of supplying. The invention therefore also relates to simple means for creating a flow of electrolyte through the flexible conduits and'the :mouthpiece. According to this aspect of the invention, the flexibleconduits from the handle are'connected individually to two tanks which are mounted in a case in such a manner that in one position of the latter there is created a difference of level between the tanks, causing electrolyte to flow from one tank through the mouthpiece to the other tank, while in another position of the case an opposite difference of level between the tanks is created causing a return flow of electrolyte from the second to the first tank through a direct conduit connection between the two tanks provided for this purpose.

By making oneself independent of other apparatuses for causing the circulation of electrolyte, it becomes also possible to operate at a pressure below that of the atmosphere in the mouthpiece so that the electrolyte is not inclined to drain off if the handle happens to be lifted from the workpiece during the process. For this purpose, according to one embodiment of the invention, the flexible conduits from the handle are individually connected to two tanks, one of which is sealingly closed and provided with a rubber ball or the like means for subjecting the tank .to a slight pressure or vacuum, while the other tank is in open communication with the atmosphere, a conduit connection being provided between the two tanks and comprising a valve, which only permits a flow of liquid in the direction from the closed towards the open tank.

The invention will now be described in further detail with reference to the accompanying drawing, in which:

Fig. l diagrammatically shows a longitudinal section through one form of a handle with mouthpiece and combined liquid flow interrupter and electrical switch forming part of an apparatus according to the invention,

Fig. 2 on a larger scale a longitudinal section through the mouthpiece,

Fig. 3 the mouthpiece of Fig. 2, as viewed from the bot tom,

Fig. 4 a developed section along the line lV-IV of Fig. 2,

Fig.5 diagrammatically one form of a case with tanks for causing the flow of electrolyte, as viewed in its operating position,

Fig. 6 the same as viewed in its position of transportation, and

Fig. 7 another form of an equipment for causing the flow of electrolyte.

In the drawing, 1 is a handle, which at its front end is constructed with an inclined bore, in which a pin 2 is rotatably mounted which at its outwardly and downwardly directed end carries a mouthpiece 3. The outer end of the pin 2 carrying the mouthpiece 3 is bent in such a manner that the axis of the pin 2 intersects the axis of the mouthpiece in a point in the vicinity of the lower end of the mouthpiece intended to be engaged with the surface of the workpiece. Through this mounting of the mouthpiece it becomes easier to engage the latter sealingly with the workpiece than if the mouthpiece were rigidly mounted on the handle, and since the axis of the pin 2 will substantially extend through the area of contact between the mouthpiece and the workpiece, a stable engagement of the mouthpiece with the workpiece is obtained. The described mounting of the mouthpiece could also be replaced by another form of articulated joint, which might comprise a universal joint, if desired.

The detailed construction of the mouth-piece is apparent from Figs. 2, 3 and 4. As will be seen, the mouth piece consists of a metallic sleeve 4, at the front end of which an .elastic sleeve 5, e. g. of a plastic material not subject to damage from electrolyte, is provided. The metallic sleeve 4 is constructed with two co-axial passages, the inner one 6 of which is formed by a tube 7 extending through the metallic sleeve and serving at its outward and as a fitting for the connection of aflexible tube 8. The outer passage 9 is formed by a bore in the metallic sleeve, in which there is mounted an inclined upwardly directed pipe for the connection .of a flexible tube. The passages 6 and 9 are open at the bottom end of the metallic sleeve .4, below which a chamber 11 is formed, which is surrounded by the elastic sleeve 5. 'In the mouth of the passage '9 there is provided a flange 12, which may be integral with the tube 7, and is constructed with a plurality of inclined passage openings 13. A flexible tube 14 is connected to the :pipe:8 anda 'flexibletube 1510 the pipe 10. Both :of .these'flexible tubes extend lengthwise through the mouthpiece and are continued from the rear end of the latter by suitable lengths of flexible tube for connection to anapparatus for causing an electrolyte to flow through the flexible tube .15

and the mouthpiece 3 and back through the flexible tube 14.

A lever 16 is pivoted to the handle at '17 and has one end thereof extending upwards from the handle, while at its other end carrying a roll 18 serving as a squeezing member for squeezing the flexible tubes 14 and 15. To

the -'arm of the lever 16 extending upwards from-the pivot 17 there is connected a compressional spring 19. This compressional spring tends to keepthe lever 16 in the position shown in the drawing, ,in which the roll 18 squeezes the flexible tubes 14 and and thereby prevents the circulation of electrolyte through the latter. By means of a finger of the hand, in which the handle is held, the lever 16 can be moved to the position shown in dotted lines, in which the roll 18 liberates the flexible tubes 14 and 15 so as to permit electrolyte to circulate through the latter.

In the handle there is also mounted a pair of contact springs 20, one of which is provided with a nose 21'lying in the path of the lowerend of the lever 16, so that the "latter will strike the nose 21 and thereby close the contacts .towards the end of its movement from the position shown in full lines to the position shown in dotted lines.

The contact springs are interposed in a conductor 22 from one terminal '23 of a source-of electric current to the pin 2 and thereby to the mouthpiece 3. 'To the other terminal 24v of the source 0f electric current there is connected a conductor'ZS intended-for conthe handle 1 and applies the mouthpiece 3 to the spot of the workpiece, whereit is desired to perform an electrolytic polishing. The elastic sleeve 5 is firmly engaged with the workpiece-and owing toits .elasticity iscapable of adjusting itselftothe shapethereof so that'it will be possible to rtreat notonlyplane surfaces-but alsosu-rfaces having a certain amount of curvature in one or more directions. By means of a finger of the hand, in which the handle 1 is held, the lever 16 is moved from the position shown in full lines to the position shown in dotted lines. The more the lever approaches the last named position, the shorter will be the arm on which the compressional spring 19 acts, and consequently only a relatively small force will be needed for keeping the lever in the turned down position in which it is to remain as long as the electrolytic polishing is being conducted. As soon as the squeezing of the flexible tubes 14 and 15 under the influence of the roll 18 ceases, electrolyte will commence to circulate from the flexible tube 15 through the mouthpiece 3 to the flexible tube 14. The electrolyte enters into the mouthpiece through the pipe 10 and then flows through the outer passage and the inclined passage openings 13 into the chamber 11 and from there back through the inner passage 6 to the flexible tube 14. As will be seen, the flow of electrolyte in the chamber 11 is directed inwardly from the circumference, while at the same time the passage through the inclined openings 6 '13 imparts a circular movement to the electrolyte. 'It has been found that this type of flow will result in a suitable sweeping of the'whole of the area=surrounded by the elastic sleeve 5 so that a uniformpolishing is obtained over substantially the wholeof the area ofithe workpiece covered by the opening .of the mouth-piece.

The electrolytic polishing can only be started from the moment when the 'lever .16 closes the contacts 20, and is interrupted again as soonas-the lever ;16 is released, whereby the electric circuit is .first interrupted and the flexible tubes 14 and '15 are thereafter squeezed by means of the roll 18 so that also the liquid .circuitis interrupted, whereafter the mouthpiece can be lifted away from the surface of the workpiece. It is to 'be observed that the contacts-20 are only intended as.a safety switch, the control of the current being normally performed at a current supply equipment having a timing arrangement. If no such current supply equipment is available, or it is in special circumstances inconvenient to use it, the control of the current may be performed 'by means of the contacts 20. It will be seen that the roll '18 in :the process of squeezing the flexible tubes 14 and .15 will sweep along the latter in a direction away from the mouth-piece whereby the electrolyte is slightly sucked away fromthe mouthpiece and theztendency to dripping from the latter is consequently minimized. During .the return stroke of the lever 16, the arm on which the compressional spring 19 actsbecomes gradually longer, :while at the same time the arm, on which the resistance of .the flexible tubes against squeezing acts, becomes gradually shorter so thata very efi'icient squeezing .is obtained in the final position of this movement indicatedin full lines in the drawing.

:Figs. ,5 and 6 show an apparatus that maybe used to obtain the circulation of electrolyte. The apparatus con sists of a case 26 in which two tanks 27 and 28 are mounted. The case is intended to be placed -.in either one of two different positions shown in :Figs. 5 and 6:respectively, and is provided with two'handles 29 and 30, by means of which the case can beplaced or carried in one and the other of these two 'positionsirespectively.

Tubes 31 and32 are connected to the tanks '27 :and'28, of which tubes the tormerextends from 'the bottom of the tank '27 whenthecase -is,inthe'positionillustrated in Fig. 5, while the tube '32 extends down into the tank28 from the upper end thereof. The tubes 31 and 32 :are intended for the connection of :the flexible tubes '15 and 14 respectively, and it will be seen that when electrolytic liquidispresent-in the tank 27, this-willbe capable, owing to the difference of level betweenthe tanks 27 and 28, to flow through the tube 31, the flexible tube '15, the mouthpiece 3, the flexible tube 14 'an'dthetube '32 down into the tank '28. As long as the whole tube system is full of electrolyte, this flow-will be independent ofthe levelat which the handle with=the mouth piece is held relative to the case. A tube 33 is also provided directly between the tanks 27 and 28, the said tube being connected in such a manner that in the position of the case shown in Fig. 5 there will be no flow of electrolyte therethrough. On the other hand, in the position of the case illustrated in Fig. 6, the tube 33 connects the bottom end of the tank 28 with the bottom end of the tank 27, and since in this position the tank 28 is located at a higher level than the tank 27, the electrolyte will flow from the tank 28 to the tank 27 so that the system is thereafter ready for being used again in the manner illustrated in Fig. 5.

Fig. 7 shows another example of an apparatus, by means of which the flow of electrolyte may be created. In this figure, 34 and 35 are two tanks, of which the tank 34 is sealingly closed, while the tank 35 is in open communication with the atmosphere through a tube 36. The tube 36 is so located, and the maximum quantity of liquid in the tank 35 so selected, that the liquid cannot end. Moreover, the flexible tube 15 is connected to the tank 35 and the flexible tube 14 to the tank 34.

The function of the apparatus illustrated in Fig. 7 is as follows: Before the apparatus is taken into use, a certain quantity of liquid is present in each of the tanks 34 and 35. If a pressure is now exerted on the rubber ball 37, a pressure above that of the atmosphere is produced in the tank 34, and under the influence of this pressure electrolyte is pressed through the pipe 38 into the tank 35, which latter remains at atmospheric pressure because it is in open communication with the atmosphere through the tube 36. When releasing the rubber ball 37, the latter will again expand to its normal shape and will therefore produce a vacuum in the tank 34, because the valve 39 prevents a return flow of electrolyte from the tank 35 to the tank 34. The apparatus is now ready for carrying out an electrolytic polishing. When the flexible tubes 15 and 14 are opened by means of the lever 16 of the handle 1, electrolyte will flow from the tank 35 through the flexible tubes 15 and 14 and the mouthpiece lying between the latter to the tank 34 under the influence of the pressure difference between the tanks 34 and 35. If during the electrolytic polishing the mouth piece happens to be lifted a little from the surface of the work piece, no electrolyte will flow out, because the mouth piece is at a vacuum.

We claim:

1. An apparatus for electrolytically polishing limited surface portions of a metallic workpiece, comprising a handle, a mouthpiece mounted on said handle, said mouthpiece having an open end to be applied to the workpiece and being constructed with two co-axial passages opening at a small distance behind said open end, a source of electrolyte, conduit means including flexible conduit portions connecting said two passages individually with said source of liquid electrolyte, means for circulating electrolyte from said source to the outer one of said two passages and back through the inner one of said two passages to said source, manually operated means mounted on said handlefor selectively permitting and cutting olf said circulation of electrolyte, and an electric circuit for creating a potential difference between the electrolyte and the workpiece.

2. An apparatus as in claim 1, in which said mouthpiece is mounted on a pin mounted in said handle for rotation about an inclined axis intersecting the axis of said mouthpiece in a point substantially in the plane of the open end thereof.

3. An apparatus as in claim 1, in which said conduit means comprise flexible liquid conduits extending from said mouthpiece through said handle, and said manually operated means comprise means for squeezing said tubes in a direction away from said mouthpiece to cut off the flow of electrolyte.

4. An apparatus as in claim 3, in which said manually operated means comprises a lever pivotally mounted in said handle and having one end thereof projecting externally of said handle to form an operating member, and a roller mounted at the other end of said lever for contacting said flexible conduits to squeeze the same.

5. An apparatus as in claim 4 including a spring biasing said lever towards the position at which said conduits are closed, the pivotal movement of said lever toward non-squeezing position decreasing the elfective moment arm of the spring with respect thereto.

6. An apparatus as in claim 1 including guiding means provided in the outer one of said two co-axial passages for imparting circular movement about the axis of the mouthpiece to the liquid electrolyte emerging from the annular opening of said outer passage.

7. An apparatus as in claim 1, in which the wall of the part of said mouthpiece extending beyond the mouths of said co-axial passages is formed of an elastic material.

8. An apparatus as in claim 1, in which said electric circuit includes a switch mounted on said handle, which switch is closed by said manually operated means towards the end of its movement to permit flow of electrolyte.

9. An apparatus as in claim 1, in which said source of electrolyte comprises two tanks, one of which is closed from the atmosphere and includes a manually operable resiliently compressible compartment, while the other tank is in open communication with the atmosphere, a conduit connection between the two tanks, said connection comprising a valve which permits a flow of liquid only in the direction from the closed towards the open tank, said conduit means connecting the outer one of said two co-axial passages with said open tank and connecting the inner one of said two co-axial passages with said closed tank.

References Cited in the file of this patent UNITED STATES PATENTS 2,080,234 Schlotter May 11, 1937 2,698,832 Swanson Jan. 4, 1955 FOREIGN PATENTS 672,698 Germany Mar. 8, 1939 921,192 France Jan. 10, 1947 26,504 Great Britain Nov. 18, 1912.

Claims (1)

1. AN APPARATUS FOR ELECTROLYTICALLY POLISHING LIMITED SURFACE PORTION OF A METALLIC WORKPIECE, COMPRISING A HANDLE, A MOUTHPIECE MOUNTED ON SAID HANDLE, SAID MOUNTHPIECE HAVING AN OPEN END TO BE APPLIED TO THE WORKPIECE AND BEING CONSTRUCTED WITH TWO CO-AXIAL PASSAGES OPENING AT A SMALL DISTANCE BEHIND SAID OPEN END, A SOURCE OF ELECTROLYTE, CONDUIT MEANS INCLUDING FLEXIBLE CONDUIT PORTION CONNECTING SAID TWO PASSAGES INDIVIDUALLY WITH SAID SOURCE OF LIQUID ELECTRLYTE, MEANS FOR CIRCULATING ELECTROLYTE FROM SAID SOURCE TO THE OUTER ONE OF SAID TWO PASSAGES AND BACK THROUGH THE INNER ONE OF SAID TWO PASSAGES TO SAID SOURCE, MANUALLY OPERATED MEANS MOUNTED ON SAID HANDLE FOR SELECTIVELY PERMITTING AND

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