Oct. 7, 1947. s. J. EVERETT 2,428,518
HYPODEHMIC TUBING, DENTAL BROACHES AND THE LIKE Filed Dec. 31, 1943 Inventor 54 40: James VIRA'77',
By QM R gmtlorney Patented Oct. 7, 1947 HYPODERMIC TUBING, DENTAL BROACHES, AND THE LIKE Samuel James Everett, Thornton Heath, England Application December 31, 1943, Serial No. 516,573
In Great Britain January 1, 1943 This invention relates to line metal articles,
such as hypodermic needles, dental breaches and the like, and to a method of manufacturing the same.
needle embodying the invention,
7 Claims. (Cl. 128221) not embodying the invention.
Figure 2B is a similar view showing a fracture One of-the disadvantages of articles of this resulting from severe bending stresses in a, needle type is that having relatively fine diameters and embodying the invention. being subjected to'bending stresses during use, g re 3 is a diagrammatic view of p t f a they are sometimes broken, thus causing injury broken dental tool embodying the invention, and to the patient. .The broken 'off pieces frequently i ures 4 and 5 a e cross-Sections, respfictively. become lodged in body tissueand being small are show g diag y, billets used in t sometimes lost or difllcult of extraction, manufacture of further implements in accord- In accordance with the present invention such ance with the invention. articles are provided with'a fibrous structure with Fi ure 1 illustrat s aphi ally the a p at n the fibers being disposed predominantly transof the invention to hypodermic needles. In thev versely to the radius on which the bending tak figure a portion of such a needle I is illustrated in place; cross section. The article is constructed prefer- Where the article for example is a hypodermic ably of austenitic nickel-chromium steel and for needle, the crystalline structure of the needle is purposes of illustration the fibrous arrangement analogous to cane or bamboo with th fibrous of the crystalline structure of the material is instructure being disposed predominantly longitudicated in dash lines 1 dinally of the needle. A hypodermic nee so It will be noted that the fibrous arrangement is constructed resists breaking into two separate predominantly longitudinally of the needle which and distinct portions to a greater degree, Severe revents the needle from breaking trans erse bending of the article may cause" the needle to into tW Sepa ate pieces when subjected to bendsplit longitudinally, but breakage into two sepaing stresses. 4 rate parts is most difilcult. Figure 2A illustrates diagrammatically what In the example of the hypodermi needle, if happens when a needle 2, as hitherto manufacthe needle is bent severely durin usage, th tured, snaps as a result of severe bending. The fibers on the outer radius may break but th metal at the outside of the bend parts at 2a while inner fibers split from the adjacent fibers so that at 2b er i a sharp k k- Further bending the inner fibers bendon an easy or substantial W ll cause the n le to n p complet ly into tWO radius such thatfthey remain intact. There is. Sep P rts. therefore, substantially no risk of the needle Figure 2B, on the other hand, shows what hapsnapping into two separate and distinct parts. Pens when a eed e Constructed acCOrding t th If the needle then breaks while in body tissue, invention snaps as a result of severe bending. there is no risk of the broken part becoming lost Again the metal at the outside of the bend snaps in the body. at 2a but the metal then splits longitudinally It is a general object of the invention to proat 20 'so that the metal at the inside of the bend vide. fine metal articles such as hypodermic neeis gently curved at 2d. Further bending will not dles, tubing, dental broaches, surgical instru- 40 substantially increase the radius of'curvature at ments, and the like, which possess this charac- 2d and there is little risk of the metal breaking teristic. I at M so that there is little risk of a part of the The invention has foranother object the proneedle being left in the patients body tissue. vision offine metal articles of-austenitic nickel- Thisproperty is due to the cane-like structure, of chromium steeL'the crystalline structureof which the metal fromwhich the needle is made. is disposed predominantly in one direction, pref- Figure 3 is a diagrammatic section through a erably at right angles to the radius onwhich the portion of a dental breach 3 according to the inbending takes place. vention, the arrangement of the fibrous crystal- These and other objects of the invention will line structure being indicated by the dash lines become more apparent from the following debearing the reference-numeral 4. Whenthe scription-and claims when read in conjunction broach is bent to such an extent that thefibers with the accompa'nyingdrawings inwhich: at the outside of the bend snap at 3a, longitudinal Figure 1 is a diagrammatic representation of splitting takes place at 30 so that the fibers on the a section taken through the end of a hypodermic inside of the bend are on a. long radius and the parts of the breach remain held together.
'may be heated for a somewhat longer time at 900 C., or heated for a shorter period at 1150 0., this being normal softening. The grain size can be controlled by the usual well known practice of quenching in oil or water.
The temperatures to which the final heating is carried in order to remove the stress or strain within the material may be varied but it is desired that this should be accomplished without destroying the fibrous structure which the material has at that time acquired. Thus, the article may be heated for a fairly long period at a temperature as low as 350 0., or for a shorter period as high as 475 C. In general, it may be said that experiments show that for most requirements the temperature should be about 400 C. for about two seconds for'every one thousandth of an inch cross-sectional dimension, as for example, wall thickness of a tube or the diameter of a breach. If the heating is done at too low a temperature or too quickly, the required stability of the crystalline metallic structure is not obtained.
The type of austenitic nickel-chromium steel employed in making articles in accordance with the invention may vary within limits. However, the following is an example of the type of steel which can be employed advantageously: Firths D. D. Q. steel containing 12% nickel and 12% chromium, the remainder being iron with traces of carbon and silicon. The steel should possess a high degree of resiliency and spring temper and great strength. Steels containing 18% nickel and 8% chromium can be cold worked to produce the required structure but are not so satisfactory in regard to their mechanical properties.
In producing fine tubing such as is employed in making hypodermic needles the following process is given by way of example: A billet of austenitic nickel-chromium steel is first drilled and by normal drawing process is then, reduced until it has an outside diameter of approximately actually made about 0.008 inch smaller than the bore. The tube can then be cold drawn to 20 gauge, that is, 0.036 inch outside diameter. It is then straightened and heat treated at 400 C. for fifteen minutes to soften the brass mandrel and improve the structure of the steel. Finally, the tubing is divided into convenient lengths with out, however, cutting the mandrel and the lengths are then drawn off the mandrel. The resulting lengths of tubing are found to have the longitudinal fibrous structure required. A similar method may be employed for the manufacture of dental broaches and similar fine steel instruments which are subjected to stresses approaching their ulti= mate strength, thereby eliminating the ever-present danger of losing a portion of the instrument I in the tissue of the body or cavity which is being operated upon.
It is. of course, a fact that the instrument when broken cannot always be pulled directly from the cavity or tissue, but the strong adherence of the broken part to the shank or remainder of the instrument enables the surgeon to make an incision in the correct place so that the parts can be successfully withdrawn.
In a modification of the aforesaid example, the initial billet, which may be half an inch to la inch in diameter, may comprise a sheath 8 of austenitic nickel-chromium steel over a tube 9 of stainless carbon steel, as shown in Figure 4. Heat treating at 1000" 0., followed by air quenching softens the outer tube and hardens the inner one. An internal corrosion resisting lining in may be provided by providing inside the initial billet, a layer of nickel-silver, silver or nickelchromium stainless steel. After the heat treatment, the composite billet is of course subjected to the extreme reduction in cross-section without further re-heating, as in the preceding example, to provide the austenitic nickel-chromium steel with the required fibrous or cane-like structure and thereby impart the required mechanical properties. To add to the fibrous structure high tensile wires II are embedded in the soft external sheath, the wires becoming integral with the tube wall during the extensive drawing oper ations. The final cane-like structure may also be enhanced by milling longitudinal slots in the initial billet.
As a variation of the methods just described, the fibrous structure of the tubing may be enhanced by building up the initial tubular billets from segments 92 (Figure 5) brazed together at their edges, the brazed joints i3 being not quite so strong as the segments themselves. If desired the segments can be composed of different metals.,
,the internal strain.
It will be understood that some changes may be made in the invention and that the description given in the accompanying illustrations are only to be considered as examples.
1. An elongated surgical member of substantially reduced cross section and which is normally subjected during use to bending strains, said member being of austenitic nickel-chromium steel, the crystalline structure'of the steel inthe finished article being comprised of parallel elongated fibers disposed predominantly parallel to the longitudinal axis of saidelongated member.
2. A surgical device or the like comprising an elongated thin steel body of cane-like fibrous structure comprised of longitudinally arranged elongated crystals, said longitudinallynrrang'ed elongated crystals being disposed substantially parallel to the longitudinal axis of said elongated steel body. 1
3. A surgical device or the like comprising an elongated austenitic nickel-chromium steel member of materially reduced cross section, said member having a predominantly longitudinal crystalline structure, ready to split longitudinally on bending.
4. A surgical device of austenitic nickel-chro- 5 mium steel, said device being elongated and having a reduced cross sectional diameter substansheath of austenitic nickel-chromium steel, renl5 dered cane-like in structure by cold elongation in the direction of the axis of the needle.
7. A hypodermic needle comprising a tube of austenitic nickel-chromium steel rendered canelike in structure by elongation in the cold state in the direction of the axis of said needle and a highly corrosion resistant layer on the inner surface of such tube.
SAMUEL JAMES REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 2,217,602 Smith Oct. 8, 1940 10 2,208,606 Smith July 23, 1940 7 2,041,778 Peters May 26, 1936 Re. 14,820 Sallows Mar. 16, 1920 2,145,171 Giles Jan. 24, 1939 2,187,259 Barnhart Jan. 16, 1940 2,217,602 Smith Oct. 8, 1940 145,217 Leiter Dec. 2, 1873- 1,942,150 Rohn Jan. 2, 1934 OTHER REFERENCES 20 Metallurgy & Metallurgical Engineering Series,
The Structure of Metals, C. S. Barrett, pp. 446 to 448.
Transactions American Society for Metals, vol. 23, Jam-Dec. 1935, pp. 400-404.