US 2355907 A
Description (OCR text may contain errors)
Aug. 15, 1944. wA A, cox 2,355,907
METHOD AND APPARATUS FOR GRINDING AND POLISHING LIGATURES Original Filed July 24, 1940 2 Sheets-Sheet l AQ A A A%.$\\
Aug. 15, 1944. Y w, A, cox 2,355,907
METHOD AND APPARATUS FOR GRINDING AND POLISHING LIGATURES original Filed July 24, 1940 2 sheets-sneer 2 Patented Aug. 15, 1944,
METHOD ANDAPPARATUS FOR GRINDING y Y AND POLISHDIG LIGATURES Walter A. Cox, Chicago, Ill., assignor-to Johnson 85` Johnson. a corporation of New Jersey Continuation of application `Serial No. 347,280, July 24, 1940. This application November 12, 1943 Serial No. 509,968 J 9 Claims. (CL 51-103) `My invention provides for polishing surgical catgut to truly circular section and uniform gage throughout its effective length so that a strand having the maximum ldiameterallowable `under government and Aother authorized specifications,
throughout its 4le`ength'wil1 havegreater tensile strength than a strand which ,varies as much as .003" in diameter at one or more points, the tolerance permitted under such specifications.
The polishing Vof surgical catgut which has a diameter of the order of thousandths'of inches only is a necessary even though difficult operalprone to slip and knot slippage in surgic tion Vdespite the fact that. as heretofore conducted, it tends to loss of tensilestrength. Unpolished catgut is used little;n if at all.. because it is difficult to draw through tissue without serious injury to thelatter. Hand polishing `has its disadvantages and yet catgut which has been hand polished under the best conditions shows a lower lo'ss of tensile strength than catgut that Ahas been polished in the conventional or so-called European machine. In that machine an abrasive disk passes up and down the length of the strand.-
of catgut and it is quite probable that, the heat thereby generated accounts fonthe loss of tensile strength. Bethat as itv may, it is a fact that catgut polished in theconventional manner by hand or by machine has a surface texture such that when the'catgut is knotted the knots are l work can be quite serious. i
Surgical catgrttis fabricated from ribbons of animal tissue or fibers twisted togetherV in more or less helicalY form. Hence, the raw string is generally marked by relatively thick and thin sections with no particular order of arrangement and by surface irregularities;4 The breaking strengthof a A'ligature otherwise sound Vis definitely governed by its 'minimum cross-section.
In a general sense `the conventional polishing takes no account of this being directed simply to the removal of humps and other surface irregularitiesV in the doing of which it not infrequently cuts or tears .the tissue and removes portionsof the surfacey atlthe hollows as well as at the humps, at any rate, the cross-section of ,a conventional v*polished strand of catgut is notuniform/and not truly circular. l f
Prior to my invention no serious eflort'was` made to pregage the rawstock in order to determine the useful or effective minimum crosssection and to polish the string `to a truly circular cross-section comparable therewith. So far as I am advised, the practice is to polish a bunchof i raw. stringsv either by hand application of the ll wherein:
abrasive-or by spinning the strings between abrasive surfaces while grasping them endwise. The
best hand polishing often results in flat strings and, yet, hand polishing is preferred to the con.- ventional machine polishing because labor is cheaper than machine work, there is lessspoilage,'no pronounced difference in the appearance `of the4 respective products. less loss in tensile strength, and withal the operation is cheaper.
It has been reportedthat thegreater part of surgical catgut production in this country is either partially or wholly hand polished and that the tensile strength of American catgut is far above that of foreign countries. And, yet,v because ithas not heretofore been possible Vto produce a strand of catgut of truly circular section and uniform gage throughout its effective length, the variousgovernment agencies in their specications relative to the purchase of surgical catgut, allow a tolerance of .003" within a given gage. The same tolerance is specified in the U. S. Pharmacopoeia which became oilicial in September l1939.
Principal objects of the present invention are to polish strings of the nature indicated, that is 'relatively thin limp strings incapable of supporting themselves in .short lengths such as lengths, of a few inches, and to do so rapidly, economically and eciently toa true circular section in such way as to make available for surgical and other uses practically all of the raw stock in all of its inherent strength; in such way that there will be no Aforeign inclusions of the nature of grit; and in such way that the surface texl ture will be normal to the major axis of the string and fof Vpronounced smoothness; to provide for pre-gaging the rawstring and selecting for polishing units thereof accordingto the respective minimum cross-section; to provide for polishing such units by single pass through the grinding throatof a modified centerless grinder and in such way as to eliminate heat and other factors having a tendency to, impair the tensile strength of the stringi and to provide a method and means fuor achieving such objects and forproducing the Y novel strand of surgical catgut of my invention.
The nature, characteristic features and scope of the invention more readily will be understood from the following description taken in connection with.' the accompanying drawings, forming a part hereof all constituting part of this application for Letters Patent which application is `a'. continuation of my earlier led application Serial Number 35,280, led July 24, 1940, and
ticularly showing how y normal to the axis; y
Y Fig. .'7 isa -diagrammatic layout for practicingV V;my method of polishing. surgical catgut;
accordance withthe invention so that the perimeter is truly concentric to the axis throughout the` length thereof; l
Fig. 4 is a section on line 4 4 of Fig. 3 showing the smooth and substantially enamel-like surface of the polished string;
Fig. 5is a reproduction of a photomicrograph of a strand of surgical catgut which has been polished in the conventional way showing that the lands or grooves resulting from thev conventional longitudinal polishing are parallel to the axis, and also showing the presence ofnap;
.Fig 6 is a View similar to Fig. 5 of a string polished according to my practice and more parthe surface texture isv vFigli isa sectional detailof the layout; and Fig. 9 is asectional detail of the ejector.
In` the preferred practice of vmy invention I first` pre-gage.the string of raw stock and, predi- Y cated onthe results of the ypre-gaging, divide the string into unitsk for :polishing and ultimate accurate classification as #A1, #2, #3, etc., the polishing being accomplished by a modified centerless grindingor'polishing operation whereby the string unit at one pass is polished to truly circular section and uniform gage throughout its-elfective'length without impairment of tensile strength and in such way that the surface tex- Ature resulting from the unavoidable abrasion marks. will be normal to the axis.
The conventional centerless` grinderor, more accurately stated, the conventional instrumentalities for conducting the stock to and away from the grinding throat are incapable of contributing toward accomplishing the ultimate purpose of my invention. Howeverj'under my system of control of-feed-and delivery -Which is preferred in a complete system or apparatus it follows that .oncethe grinding throat is adjusted for operation on units of a certain classification, it is possible in acommercial way, that is to say', rapidly, efficiently and economically continuously to polish the units to truly circular section and uniform gage. The control comprehends apush and-pull operation, and instrumentalities for Ycarrying it into effect whereby units, other than unt or rejected units, are pushed or impelled a'nto the grinding throat and after polishing pulled therefrom, Vthe pushingand pulling instrumentalities and intervening work supports operating to maintain tension on thestring unit so as to minimize the building up of resisting forces and particularly torque in the string. Undermy system of pre-gaging. classification and control I can, by asingle pass grind and polish surgical catgut to an uniform circular section, the total variation being substantially not more than 0.0005". 1
It is a merit of the invention that the pushing or feeding system comprehends a'luid conveyer to handle the string units to be polished. Such conveyer may be either of the pneumatic or hydraulic type. It is preferred, however, to employ a hydraulic conveyer or injector because it lends itself to that part of the invention which provides for the use of a cooling medium to prevent or substantially inhibit the generation of ing or injecting instrumentality is of the hydraulic type, the ejector will, by, preference, be
. of the' pneumatic type in order to substantially the machine cycle.
effect the drying of the polished units during It will be understood then,`having reference to Pig. 1, that the raw or unpolished strand 5 is pre-gaged and marked according to its variable areas of minimum cross-section for ultimate division and classification of unpolished units or sections. For example, assuming that the string is twenty feet long, it is pre-gagedinto say, four 5-foot sections and, since the 'minimum diameter is the factor that determines the size to which the string is to be ground and polished, two sections ,may serve for #l string andthe other sections for #2 and #3, respectively... Fig. 2 shows in contrast broken sections of the pregaged unit having a maximum diameter vof .028" and a minimum diameter of .0235". Such and other unpolished units are separated according to classificationfand it will bek evident that thenot contain'inferior material, has .been properly made and dried, and so long as no plies are cut in the polishing process. It follows that if a polishing process for the production of, say, #2 sutures is set up so that the averagesize ofr the suture is 0.021 (the upper limit of #2) `and if, further, the sutures produced have a maximum totalvariation of 0.003", then the strength of such a suture will be determined by the strength of its minimum section, i. e., onewhose diameter is`0.0195", and the .maximum size of the suture will be 0.0225, or a size equivalent to a #3. In other words, the resultant suture will be an oversize #2 with the strength of light #2. If the maximum total variation in diameter were reduced to, say, 0.0005, then the diameter would range between 0.02075 and 0.02125, Vthe strength would be determined `by the 0.02075" section and the whole. suture would be sized as a full #2. From this it follows that a decrease in the diametric variation of .a suture, while notconstituting an improvement in the inherent strength of the material should, nevertheless, improve the effective strength of any given size. Demonstration has proved this to be the case. [t may be mentioned that variations of from 0.003" to 0.005" are usual in material polished by hand or by the conventional machine method. A #2 string is a relatively large size string and, hence, the percentage increase in minimum area is even more marked in the smaller sizes.
Figs. 3 and 4 show the blank of Fig. 2 polished to an even and uniform diameter and having a surface devoid of nap and smooth and lsubstantialiy venamel-like as indicated at 6.
Fig. 5 shows a string that has been ground and polished inthe conventional way and characterized by the non-uniformity of its diameter, by the presence of lands or grooves 1, due to the ".'longltudlnal polishing, ranging parallel to string axis, :and `further `characterized by the presence of'fuzz or nap.
be Jair, water;V lard'oil,
j am Vthe guide 'than the hydraulic type'. :principally to providefor the (Fig. v6Y shows a'sir'nilarstrin'g grroundby the VL'n'iethod of myinvention, characterized by its u'ni- "form diameter, its smooth surface, and by the V@fact that ltssurface texture is normal to its axis :as-indicatedva'tl. o o
Referring to -the diagrammatic layout, Fig. '7,
the numeral fil indicates a grinding wheel and l0 La regulating-wheelcustomary in a so called-cen- .'fterless :grinder and relatively ladjustable tofpro- #avide `a Vvariable grinding throat II- 'The `cus- :gtomaryigrindingthroat is modifiedtoprovide suitablework supports orinstrumentalities l2 `which"participate in *the adjustment stated for .determining the gage of polishing `and. toi sustain 4the string'units against whipping ,or vibrating pro'priate wayand having an outlet or nozzle lI5 Y Vwhich "feeds the` units 'to the grinding throat.
' Nozzle I5' may be any appropriate type of Vfluid `irriector,-for example, the injector shown in Fig.
Shaving an axial bore i6 serving as a vstring or -rwork conduit, and a port il forthe admission r:of a;highzv'elocity stream offluid.V The uid Vmay etc..bu,t, as beforeistated, v"I prefer to usea cooling medium suchas a hy- ,drocarbonl liquid or gas. 'ls an -excellent cooling medium,V is effective to 'swash :away the-polishing debris and being volatilemakes-for rapid drying of theV polished unit.
For example, "Cumol A.coolingsubstance of theV type indicatedfconfers upon Athe polished `string a'V substantially A.smooth and somewhat enamel-like 4also iseffective asasterilizing agenti surface, and
AAt-fsome point conveniently located inthe -string `guidecr conduit" I 3 there is provided, as -at 1,8,..any` appropriateV form" of gage or otherconventional deviceffor rejecting lumpy or defec- .tives'tringunitsor for indicating the presence of units which,fif permitted to pass that point, might or the grinding throat and so interrupt the'continuity of the machine operation.
-Intermediate the rejecting station and the in- .Jector is a suitable control or pressure reducer 1I-S for regulating the action of the injector.
On` the delivery side of the grinding throat there is a. stringreceiving and pulling device comprising a blastor ejector nozzle'Zll of any suitable well-,known type communicating with a discharge conduit 2|; It will be understood that nozzle .20 maybe regulated in anyl well known Y `manner to vary the pressure volume of the air or other Vfluid medium; In spite of lowere'fflcienc'ies the ejectorispreferably of the pneumatic rather Thischoice is made polished ligature as itpasses througntheejector,
vthus eliminating the necessity of a separate drylng` operation after the grinding orpolishing operation. Actually the drying takes place in two .distinct phases. As the rapidly rotating string .passes the gap between the injection and ejection tubes, the excess' coolant is removed by centrlfugal force. .The vremaining surface coating of vcoolant is evaporated by the action of the air blast in the ejector nozzle. The Vejector is so' designed and arranged that there is a slight posi- Y tivepressure at the inlet. If the pressure at that point were negative, part of the coolant-laden atmosphere in the grinding throat would be drying the ground or" d rawuolf, the evaporating` efficiency of the nozzle Vwould be reduced to a -pointfwhere :wet-.strings would result,V and a lcertain lamounto'f coolant would be continuously lost.
It will be understood that-.duringfthe .polishing operation the rotation and travel ofV thestring are controlled by wheel action within the A.grinding throat and in the. preferred form of apparatus by the coordinate Vactionof the propelling and pulling instrumentalitles in conjunction -with the o `Work supports which maintain-the :centerline of grinding or polishing. `The leading end `iof-:the
V whilebeing axiauylfed atrelatively highspeed A-zfandwhile rotating athighz speed. Y At i3 is indi- 'fcated a tubular conduit having anirilet I4 to which Athe string units are -directed in any ap- "string being fed followsclosely the trailinglend Y of thestring Vbeing polished. While itis `occupying Vthe grinding throat. the .string is Vunder :pushingjaction ofitheinjector and pulling-,action of the" ejector when these preferred finstrumentalities are used. One effectof this: duringeextreme [instances of polishing is to prevent4 the'string from stallingin thegrinding throat shouldit be 4one that has passed inspection and yet containsV an undersize section of a length greater vthan the Y length of thegrinding throat, i. e.,' afsectionwhose have devised `a method and means `whereby-sur- 'diameter isless thanthat of ,thegrindingthroat It will be apparent from .the foregoing `thatI gicalsutures are `pre-.gaged and sorted: .for -polishing and' arepolishedto true circular section and uniformity'oflgage, the tolerance or..tota.l
variation being substantially not moreuthan 0.0005" in contrastto government and other authorized tolerance'of .003". p
` The polishing `is effected funder..;conditions Moreover,.
which inhibit loss of. tensile strength; astrand `of catgut having .the maximumdiameter, allowable under government or other authority. uniformly throughout its-length will have greater ltensilestrength than a. strand which varies as much asA .0035 in diameter -at one or more points.
The precision productoffmy invention makes for accurate and dependable labelingsothat the surgeon need no longer be under .apprehension that he is working with a wrong size or `doubtful Heretofore, and prior to my invention, surgical catgut labels afforded no laccurate guide as to sizeand strength. f In short, thesurgeon could but ask for a certainnumber, for example, #2, and he might and might not get a suture strong enough for his purpose because .003"
Y tolerance is .allowed in each sizeand that variation'between the feed line and the grinding throat and effective to supply wet stock to the vgrinding throat, and an ejector of the dry type on the other side of the grinding throat and effective to receive and dry the polished stock.
2. In an apparatus for polishing fiexible strings t0 insure a uniformly round section and apol- V ished surface characterized by ridges normal to the lengthwise axis of the strings, the combination comprising a grinding wheel, Va regulating wheel, a string support providing a grinding throat, and aligned fluid injector and ejector del vices for controlling the movement of the strings v 'abouty itsv longitudinal axis.
vancing said element longitudinally through said` zone, restricting said element while in said zone Y against any appreciable movement out of its 'longitudinal path, and grinding orv polishing the element fwhilerinsaid zone 'and as it is rotated 4'. The metnqdffof 'lnaiicllingY al'imp, pliable;
Y .Y Vcord-'like element,fsuch as a suture, to render it substantially uniform in diameter by grinding or polishingwhich method includes conveying -s'aid'eleme'nt by the action of a bodyof fluid polishing which method includes conveying said element by the action of a body of fluid surround- `ing said element and moving in a direction to or polishing the element while in said zone, and Y simultaneously conveying said element away from said zone and drying said element.
' 8. The method of grinding an individual length 'of a cord-like element to render said Yelement substantiallyfuniform in diameter which method includes the steps of continuously advancing an individual length of a limp pliable cord-like element, suchfas a. suture having a diameterof the order of thousandths of an inch and which when Auntensioned is incapable of self-support, longitusurrounding said element and moving in a direc'- tionto convey the 'element longitudinally toward a grinding-or polishing zone, continuously ad- VanCin'g-'SaidfeIement longitudinallyvthrough said zone; restricting said element while in said zone :i against"Y any appreciable-movement out of its longitudinal pathjgrinding or polishing the ele- 'ment while in said' zoneand conveying said elemerit longitudinally by the'action `of a body of 'uid surrounding said element and movingin a direction away from said zone.
r5`1-The"method `of handling a limp, pliable, cord-like element, such as a suture, to render it substantially uniform in diameter by grinding or polishing which-method includes conveying said elemen'tfby `the action of a, bodyrof liquid surrounding said element and moving in a direction to convey-the element longitudinally toward a grinding or polishing zone, continuously advanc- -ingwsaidelement longitudinally through said zone, restricting said element while in said zone against any appreciable movement out of its longitudinal path and grindingor polishing the element while in said zone and as it is rotated about .its longitudinal axis;
/ eiThe method of handling a limp, pliable, cordflike element, such as avsuture, to render it substantially uniform in diameter by grinding or.
gitudinal path, grinding or polishing the elementV while in said zone, and conveying said element longitudinally bythe'action of a body of air surrounding said element and moving in a direc- Vtioniaway from said zone.
7. The methodof handling a limp, pliable cord-likeelement, such as a suture, to render it substantially uniform in diameter by grinding or dinally through a grindingV or polishing zone, positively restricting said element `while in said zone against any appreciable movement out of lits longitudinal path, and lgrinding or polishing the surface of said element transversely to its longitudinal'axis whileV rotating the element about said axis, the longitudinal movement through the grinding zone and the rotational movement of said element being effected simultaneously and by engagement vof the grinding or polishing media with that portion of said element in the grinding zone of a diameter greater than will p ermit free passage through said zone, vthe ends of said limp element being maintainedV free so as to permit said longitudinal and rotational movement.
9. The method of handlingv an individual lengthof a cord-likeelement to render said suture substantially uniform in diameter by grinding or polishing which method includes the steps o f conveying an individual length of a limp pliable cord-like element such as a suture having a diameter of the order of thousandths'of an inch and which when untensioned is incapable of selfsupport, longitudinally toward a grinding or polishing zone, continuously advancing said individual -element'longitudinally through `said zone, positively restricting saidvelement while in said zone against any appreciable movement out of 4its longitudinal path, grinding and polishing said element transversely to its longitudinal axis while rotating said element vabouttits longitudinal axis, and conveying said Velement longitudinally away from said zone, said limp element being supported exteriorly of and adjacent both ends of said zone to facilitate its longitudinal movement as it is Vconveyed toward and away from said zone, the ends of said element being maintained free so as to permitthe longitudinal movement through the grinding zone and rotational movement of the element in said zone' which movements are effected simultaneously by engagement of the grinding or polishing media with that portion of -the element within the grinding zone and of a diameter greater than will permit free passage through said zone- WALTER. A. COX.V