US3701725A - Apparatus for electropolishing of drilled surgical needles - Google Patents

Abstract

A LARGE NUMBER OF STEEL SURGICAL NEEDLES ARE SUPPORTED ON A PLATINUM GAUZE ANODE IN A MAGNETIC FIELD AND IMMERSED IN AN ORTHOPHOSPHORIC ACID ELECTROPOLISHING BATH. THE NEEDLES SUPPORTED ON THE ANODE ARE POLISHED BY A CURRENT THAT FLOWS THROUGH THE SOLUTION, AND NEEDLES TO

PRODUCE A SMOOTH NEEDLE SURFACE THAT IS FREE OF FLAWS AT THE POINT OF CONTACT WITH OTHER NEEDLES ON THE ANODE.

Description

Oct. 31, 1972 BEROFF EI'AL 3,701,725

APPARATUS FOR ELECTROPOLISHING 0F DRILLED SURGICAL NEEDLES o1-1g1na1 Filed Jan. 29, 1970 4 Sheets-Sheet 1 Oct. 31, 1972 BERQFF EI'AL 3,701,725

APPARATUS FOR ELECTROPOLISHING 0F DRILLED SURGICAL NEEDLES 4 Sheets-Sheet 2 Original Filed Jan. 29, 1970 IN VEN T O R 0.7 //OW/I?D BfFOl-F [P/VE'STL Homo/m QMAWL A TTORNE Y Oct. 31; 1972 BERQFF ETAL APPARATUS FOR ELECTROPOLISHING 0F DRILLED SURGICAL NEEDLES Original Filed Jan. 29, 1970 4 Sheets-Sheet 5 EFH a Q l'h/WOND KM M41 ATTOPNF) uni i .llllL Oct. 31, 1 972 H BERQFF ETAL APPARATUS FOR ELECTROPOLISHING OF DRILLED SURGICAL NEEDLES 4 Sheets-Sheet 4 Original Filed Jan. 29, 1970 Jt i 17 mvmwom HOWAEDEfPO/F FP/VEsrL IL'HMOND United States Patent U.S. Cl. 204297 M 4 Claims ABSTRACT OF THE DISCLOSURE A large number of steel surgical needles are supported on a platinum gauze anode in a magnetic field and immersed in an orthophosphoric acid electropolishing bath. The needles supported on the anode are polished by a current that flows through the solution, and needles to produce a smooth needle surface that is free of flaws at the point of contact with other needles on the anode.

BACKGROUND OF THE INVENTION This patent application is a division of copending, commonly-assigned patent application, Ser. No. 6,878, filed I an. 29, 1970 and now abandoned.

The present invention relates to the electropolishing of surgical needles and more particularly to an improved apparatus for the electropolishing of drilled stainless steel needles. The needles produced by the apparatus of the present invention are free of small surface imperfections and have a mirror-like finish.

In the modern operating room there is available to the operating surgeon a variety of suture materials having affixed to one end thereof a surgical needle of the proper size and shape for the operation in progress. Thus, hundreds of thousands of surgical needles may be used every day in hospitals throughout the United States and are discarded after use to insure sharpness and to avoid the problems of resterilization.

Surgical needles are generally formed of stainless steel in order to resist the corrosion that may occur during storage in the tubing fluid. A preferred form of needle is a drilled needle, which has a concentric cylindrical hole drilled in the blunt end of the needle. Such needles are formed from stainless steel wire which is straightened and cut to form a blank, one end of which is then die-formed to produce a cutting edge or point. The cutting edges are then ground until sharp. Finally, the needle is formed to the desired shape and heat treated to improve the temper (increase the hardness of the needle without impairing brittleness). During this heat treatment step, the needles will frequently become discolored with a coating of oxide or scale that is removed in the polishing process.

It is well known among those skilled in the art of needle making that surgical needles subsequent to sharpening and tempering may be polished electrolytically by immersing the needle in an acid solution and passing a direct current through the solution and the needle being polished. The scale and discoloration that may result from the heat treatment is thereby removed and the needle is polished in that small surface imperfections are removed by anodic dissolution of metal. The electropolishing of surgical needles has always been an expensive and time consuming process, however, because it was necessary to exercise great care in supporting the needle within the polishing bath. One method of supporting the needles during the polishing step uses a magnetic needle rack as described in US. Pat. No. 3,268,428. It is a disadvantage of the magnetic rack described in that patent, however, that the precise positioning of the needle on the face of the magnet is a time consuming hand operation.

Another method of supporting surgical needles within the electrolytic polishing bath that has been used by the assignee of the present application in the manufacture of surgical needles was to secure the drilled end of the needle in a conductive metal clip. The needle is then placed below the surface of the electropolishing bath so that the entire needle surface is polished, except for the drilled end which contacts the clip. Again, however, a time consuming operation is involved since each individual needle must be precisely placed in its corresponding supporting clip so that the clip contacts the needle surface only at its remote drilled end. This precaution is necessary because the needle will be etched and roughened at the point of contact with its supporting clip. By supporting the needle at the butt end such imperfections are of minimum concern since the marks made during the electropolishing step are generally obscured during the swaging of the drilled needle to the suture material.

It has now been discovered that stainless steel surgical needles may be electropolished in large batches by placing a substantial number of such needles in an electrolytic fluid on a platinum polishing anode in random arrangement. The steel needles are held against the platinum surface of the anode by magnetic force. While one would have expected that needles polished in this manner would have surface imperfections and cross-over marks on those areas in contact with adjacent needles during the polishing step, this did not occur. The process to be described reduces the time that is required for polishing since it is unnecessary to handle each individual needle. Moreover, it is possible to control the process to be described so accurately that less than 0.0005 inch of material is removed. Inasmuch as the diameter of surgical needles is controlled to within 0.001 inch, it is now possible for the first time to repolish a needle that retains a slight surface imperfection without removing more than the 0.001 inch permitted by quality control specifications. The object of the invention, therefore, is to provide a fast and reliable method for polishing a plurality of stainless steel needles in large batches whereby scale and surface imperfections that are present following the heat treating step are removed to provide a bright uniformly polished surface that is devoid of etching and cross-over marks.

The foregoing object may be attained in accordance with the present invention which provides a novel electropolishing apparatus comprising an anode that is rectangular in cross-section having a magnetic central core. The central core has a titanium metal frame to which is secured a plurality of small ceramic magnets. The magnets serve the important function of retaining the needles to be polished in electrical contact with the surface of the anode and each other, and are part of a hinged assembly which permits the operator to discharge the needles after the polishing operation by swinging the surface of the anode and the needles supported thereon out of the magnetic field.

The apparatus of the present invention permits one to Y polish a large batch of needles, i.e. 200 to 3,000 at one time, depending upon the size of the needles. The needles to be polished may be scattered over the anode surface from a large container and discharged from the anode without the tedious and time consuming hand operations formerly employed.

The polishing anode is designed for the rapid polishing of surgical needles and its construction is such that the needles contact only the exterior platinum surfaces of the anode and each other. It has been discovered that a platinum surface is required to obtain the desired mirrorlike polish on the needles. Other materials investigated did not produce polished needles of the same quality.

Particularly preferred as the anode surface is platinum gauze (No. 80 United States Standard Sieve Series, 177 micron). Alternatively, a titanium anode the surface of which is plated with platinum (matte finish) may be used.

The invention will appear more clearly from the following detailed .description when taken in connection with the accompanying drawings, which show by way of example, preferred embodiments of the inventive idea. Referring now to the drawings:

FIG. 1 isa perspective of the apparatus.

FIG. 2 shows a vertical cross-section of the unloading tray and associated parts, taken along line 2-2 of FIG. 1.

FIG. 3 is a vertical cross-section through the electrolytic bath taken on line 3-3 of FIG. 1.

FIG. 4 is an enlarged cross-section partly in elevation through one of the cathode plates and taken along line 4-4 of FIG. 3.

FIG. 5 shows a vertical cross-section of the wash tank taken along line 5-5 of FIG. 1.

FIG. 6 is a vertical face or elevational view of a magnetic tray unit; broken away in a cross-section. The righthand side being in elevation and broken away to see the screen, titanium plate, and the grill portions beyond which the fixed magnet unit is seen.

FIG. 7 is an inverted fragmental edgev elevation of FIG. 6 partly in section and partly in elevation.

FIG. 8 is an endelevation, broken away and in sec tion of the left side of FIG. 6 showing only the centrally located magnet unit.

FIG. 9 shows a perspective of one of the magnets shown in FIGS. 6 to 9. 1

FIG. 10 is an enlarged cross-section taken along line 10-10 of FIG. 6 showing the laminated structures hingeable at their upper ends, and FIG. 11 is an exploded perspective of the laminations shown in FIG. 10.

The construction of the anode assembly is best shown in FIGS. 6 through 11.' The conductive metals used to build the assembly are platinum, which forms the surface of the anode, and titanium. It has been found that titanium quickly forms a titanium oxide surface coating under the conditions of use that is highly resistant to current flow. This greatly increases the efiiciency of the polishing operation, and reduces the temperature rise of the electropolishing bath since the primary current flow is through the needles 17 being polished and the platinum support. There is very little current leakage through the titanium oxide surface of the'anode assembly.

The magnetic field that retains theneedles against the anode surface during the polishing operation may be provided by a plurality of small rectangular,- permanent magnets best illustrates in FIG. 10. If the construction of the anode is such that the magnets are in contact with the electropolishing bath suitable non-conductive ceramic magnets may be obtained from Indiana General Corporation, Valparaiso, Ind. (Indox' 5). Shallow transverse channels 16 and 16 are provided in the magnet surfaces to facilitate clamping the magnet to a central frame 18 which, together with a plurality of magnets 15, form the magnetic core 19 of the anode assembly.

The magnetic core 19 is best illustrated in FIGS. 6 through 8. It consists of the frame 18 that is rectanglar in shape; the outer dimensions being fixed by the end members 20 and 20' and the longitudinal members 21 and 21'. Extruding outwardly from the lower frame member, as viewed in FIG. 6 are cylindrical pintles 22 and 22', the function of which will be described below. The frame is divided by cross-bars 23 and longitudinal bars 24 into a series-of compartments, the dimensions of which correspond to the length and width of magnet 15. The magnets are oriented in the frame so that the north pole of each magnet is in proximity with the south pole of every adjacent magnet and are firmly secured in position by the clamping bars 26 and 26' which engage the channels 16 and 16' in the magnets 15 and are secured to the frame members 21 and 21' by screws 27 and 27'.

The top member 21 of the frame 18 is welded to vertical supports 29 that suspend the entire anode assembly from a bus bar 30.

A handle 31 is attached to the top of the bus bar and facilitates accurate positioning of the anode assembly in the electropolishing bath.

To complete the description of the anode there is positioned on both sides of the magnetic core assembly described above platinum screens 32 and '32 slightly greater in length and breadth than the frame 18.

The platinum screen 32 and a backing sheet of titanium 33,are held between a grill 34 and an outer frame 35 by the bolts 36 which engage threads in the grill 34. In a like manner, the platinum screen 32' and its backing sheet 33' are held between the grill 34 and outer frame 35 by the bolts 36 which engage threads in the grill 34'. The platinum screen surfaces and their supporting frame are hinged bymeans of hinge pins 37 and hinge brackets 38 to the vertical members 29 which support the entire electropolishing anode assembly and function to conduct current to the anode during the electropolishing operation. Small ceramic magnets 39 are mounted on the lower edge of the grills 34 and 34'. These magnets act to hold the grills 34 and 34' together so that the platinum screens are parallel to each other and to the magnetic core assembly formed by the inner frame 18, magnets 15 and clamping bars 26.

Inasmuch as the ceramic magnets are corroded by the acid electropolishing bath and have a limited commercial life, a preferred embodiment of the present invention is to encapsulate the magnetic core within a titanium container, welding all joints to prevent contact between the electropolishing bath and the magnets.

Example I.--Electropolishing of drilled /z circle stainless steel surgical needles inum surface 32 of the anode. The anode is then rotated toward the operator on the pintles 22 and 22' to the position shown in dotted lines in FIG. 2. The anode in that position is supported on the tray rests 43 and 43' with the other surface of the anode 32' facing upward. The needles on the lower surface 32 are retained by magnetic attraction.

An equal weight of surgical needles is evenly distributed in like manner over the opposite surface. The magnetic anode with the needles in place is then removed from the work table and placed in an electropolishing bath 44 between two cathodes 45 and 46. The two cathodes are similarly constructed of stainless steel as best illustrated in FIGS. 3 and 4. Individual separated cathode plates 51 are secured to the cathode bus bar 53 by'bolts 55 and 55 and extend across a ceramic vat 48 equidistant from the platinum surfaces 32 and 32' of the polishing anode. As best illustrated in FIG. 1, the magnetic anode makes electrical contact with the polishing tank bus bar 50.

The electropolishing bath is a solution containing 70 parts by weight orthophosphoric acid, 30 parts by weight hydroxyacetic acid. This electropolishing solution is contained in the ceramic vat 48.

Current is passed through the polishing bath and needles for minutes. The current flow is 72 amperes at 10 volts, and the temperature of the polishing bath is 190 F. A DC rectifier that will supply amperes at 12 volts is suitable as a power supply. 'Fumes and vapors from the electropolishing bath are carried away by the exhaust duct 65.

' After polishing for 4 minutes, the anode is removed from the polishing bath and placed on the rest ledges 49 and 49' over the polishing bath to permit the acid polishing solution to drain from the needles and anode. The anode is then transferred to a first water rinse compartment 52 of a four-station rinse tank 54. The anode and needles are rinsed in the compartment 52 for 1 minute and then transferred to the second rinse compartment 56 for another minuteto flush off any remaining polishing acid. The rinse tanks are continuously supplied with water through inlet valves 57 at a rate of 1 gallon per minute; and overflows through the exit ports 59; the temperature of the rinse water being maintained at 115 F.

After the water rinses, the anode is advanced to a third compartment 58 where the needles are submerged in a solution containing 183 parts by volume orthophosphoric acid, reagent grade; 20 parts by volume of a wetting agent (Triton X-100); and 6725 parts by volume water. This solution acts to complex any iron carried over from the polishing step and prevents discoloration of the needles. The needles are then advanced from the phosphoric acid solution to a final water rinse compartment 60, continuously supplied with warm water at the rate of 1 gallon per minute.

The anode together with the partially polished needles is then removed from the tank and supported over the drain 61 at the end of the tank 54 as shown in FIG. 5. After draining, the anode is placed over an absorbent paper towel and the platinum surface 32 is swung about the hinge pin 37 away from the magnetic core permitting the needles to drop onto the paper towel. In a similar manner, the needles on the platinum surface 32 may be collected.

The platinum screens of the anode assembly are repositioned over the magnetic core and the anode is replaced on the work table in position for loading. The partially polished needles are returned to the anode surfaces and evenly distributed as described above. The anode with the needles in place is then reinserted in the electropolishing bath and polished for an additional 3 minutes as described above. During this second polishing cycle the current flow is 70 amperes at volts. The anode is removed from the polishing bath; the needles are rinsed with water, treated with phosphoric acid solution, and washed exactly as described above.

After draining, the needles may be transferred to a fiber board tray lined with paper towels by swinging the platinum surfaces away from the magnetic core of the anode assembly. The needles in the fiber board tray are then passed over a 60 cycle alternating current magnet until the needles in the tray lay flat indicating that no residual polarity remains.

Needles polished as described above upon inspection are found to have a mirror-like surface free of cross-over marks and other imperfections. The electropolishing process removes about 0.001 inch, i.e. a needle 0.039 inch in diameter before polishing will measure about 0.038 inch in diameter after polishing.

While the invention has been described in detail according to the preferred manner of carrying out the process and manufacturing the products, it will be obvious to those skilled in the art, after understanding the invention, that changes and modifications may be made therein without departing from the spirit or scope of the invention, and it is intended in the appended claims to cover such changes and modifications.

What is claimed is: 1. Apparatus for electrically polishing steel surgical needles comprising in combination:

an anode assembly means for supporting a batch of steel surgical needles to be polished consisting of a platinum anode together with a plurality of magnets mounted on a titanium carrier and held adjacent to one surface of said platinum anode; a cathode; means adapted to contain an electrolytic polishing solution; and means for supporting said anode assembly and said cathode within said solution. 2. Apparatus in accordance with claim 1 wherein said platinum anode is a sheet of platinum gauze.

3. Apparatus for electrically polishing steel surgical needles comprising in combination:

an anode assembly means for supporting a batch of steel surgical needles to be polished consisting of a titanium sheet at least one surface of which has been coated with platinum together with a plurality of magnets mounted on a titanium carrier and held in contact with said titanium sheet; a cathode, means adapted to contain an electrolytic polishing solution, and mounts for supporting said anode assembly and said cathode within said solution. 4. Apparatus for electrically polishing steel surgical needles comprising in combination:

an anode assembly means for supporting a batch of steel surgical needles to be polished consisting of a plurality of magnets encapsulated in a titanium container; a sheet of platinum adjacent to said titanium container; a cathode, means adapted to contain an electrolytic polishing solution, and mounts for supporting said anode assembly and said cathode within said solution.

References Cited UNITED STATES PATENTS 2,732,339 1/ 1956 Webster 2042-85 2,803,595 8/1957 tAnzaldi 204297 3,000,806 9/ 1961 Marotta et al 204-285 3,038,475 6/1962 Orcutt 204142 3,268,428 8/1966 Buccino 204-142 3,457,151 7/ 1969 Kortejarvi 204-285 FOREIGN PATENTS 424,246 5/1933 Great Britain 204-497 546,465 2/1932 Germany 204-297 JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant Examiner US. Cl. X.R. 204140.5, 285

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