Abrading – Abrading process
Reexamination Certificate
1994-10-19
2001-03-27
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
C451S035000
Reexamination Certificate
active
06206755
ABSTRACT:
BACKGROUND
1. Technical Field
The method and apparatus herein described relate to the manufacture of surgical needles.
2. Background of the Art
Surgical needles are known in the art. Typically, a surgical needle has a barrel end to which a suture is attached, and a tapered end which terminates in a sharp tissue piercing point. Optionally, the needle may be ground and polished to have cutting edges as well as a sharp point.
In some applications it may be desirable to have a blunt needle without a sharp point or cutting edges. Blunt needles can have a tapered or non-tapered tissue piercing tip which is capable of penetrating delicate organs, such as the liver, or soft tissue, such as muscle, fascia, adipose, etc. An advantage of a blunt needle is that the needle does not cut friable tissue such as the liver, and may reduce the likelihood the needle may penetrate cutaneous tissue, (such as the skin of the surgeon's hand) under operating conditions where the needle is not under the surgeon's direct vision. Thus, the tip of the blunt surgical needle is adequate for certain surgical procedures performed inside the human or animal body, while protecting friable tissue and offering the surgeon a degree of safety from inadvertent needle stabs.
Ball point blunt needles and tapered blunt tip needles and their use have been known for many years. In the past blunt needles typically have been made by machining or grinding tapered needles to form a radiused blunt tip. Such a method is expensive, time consuming, and not conducive to economically producing large quantities of blunt needles at one time.
SUMMARY
A method is provided herein for producing blunt surgical needles having a radiused tip from finished or semi-finished tapered surgical needles. The blunt needles made by the method disclosed herein may be ball point or blunt taper point or blunt pointed needles of other configurations, as desired. The method comprises forming a radius at the tip of the surgical needle by a first tumbling operation in a tumbler with a first medium for a first duration of tumbling time. Optionally, the tip of the needle may be cut or ground off of the needle prior to tumbling to produce an even broader blunt tip. As yet a further alternative, the starting needle may be partially formed without completing the needle tip, such as a needle which has been tapered but the final tip configuration has not been completed. Removing a portion of the tip prior to tumbling, or starting with an incompletely formed tip, may reduce the tumbling time required to achieve the desired result. The method may include an abrasive tumbling step alone or in combination with a burnishing step. Alternatively, a burnishing tumbling step alone may be used to form a radius on the tip of the needle. In either case, burnishing preferably is performed using a hard medium such as porcelain balls. Also, an optional polishing step may be performed by tumbling with a substantially dry soft medium such as, for example, dry walnut shells, cob meal, wood pegs, etc. Tumbling may be performed in vibratory, rotary or centrifugal type tumblers. Hard media such as steel, porcelain, aluminum oxide, etc. normally are wet to aid in removal of fines, aid lubricity, and soften the tumbling process. Wet tumbling compounds may be acidic or alkaline. Various other components, such as silica or lime, may be added to the medium.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)
The method and apparatus described herein are directed to forming a radiused tip and blunting the sharp edges of surgical needles by a tumbling operation. Tumbling is described in copending U.S. application Ser. No. 08/091,545, now issued as U.S. Pat. No. 5,447,465 which is hereby incorporated by reference in its entirety.
The needles to be treated by the tumbling operation described herein may be fabricated from any material suitable for the manufacture of surgical needles. Preferred needle materials are alloys of stainless steel such as 300 and 400 series stainless steels.
The alloy is originally in the form of wire stock which is straightened (if necessary) and cut into needle blanks by processes and machinery familiar to those with skill in the art. The needle blanks typically have a diameter of from about 1.5 mils for ophthalmic needles to about 62 mils for sternum needles. A mil is one thousandth of an inch, i.e. 0.001 inches. The needle blanks may be drilled at one end, either mechanically or by laser drilling, to form an axially aligned hole therein for the reception of a surgical suture. Alternatively, the needle blanks may be channeled for suture attachment. Drilling or channeling may be performed before or after tumbling the needle blanks in accordance with the present disclosure.
Preferred are needles made from 455 stainless steel with diameters of from about 24 mils or less to about 60 mils. The needles are tapered to a finished or semi-finished point and may optionally be curved before or after tumbling.
To produce a radius on the tip of the needle the needle is tumbled in a hard medium, as explained below. The needle may be finished, i.e. already ground, and polished to a sharp point before the needle is tumbled Optionally, the point of the tapered tip may be cut off to produce a wider diameter blunt tip prior to tumbling. As yet a further alternative, the starting needle may be partially finished. By way of example, tapered needles typically are formed by subjecting the needle to a number of grinding passes, so it is contemplated that the initial taper could be formed by subjecting the needle to some but not all of the passes required to completely form the tip. Optionally, an abrasive medium may initially be used to blunt the needle tip. However, abrasive media scratch the needle surface and should be followed by tumbling with a hard medium as described below. The radiused needles may further be tumbled in a soft medium for polishing.
The particles of tumbling medium preferably should not cause excessive scratching of the needle surface. That is, the media should not reduce surface clarity in an objectionable manner. To accomplish this the tumbling medium must either have a hardness less than or equal to that of the needle blank (i.e. a “soft” medium), or the particles of tumbling medium must have a smooth surface, i.e. no sharp points or edges capable of causing a visible scratch. As distinguished from abrasive media, the preferred medium for creating a radiused tip operates by burnishing the needle rather than by abrasion and scratching. A suitable “hard” medium (i.e. one having a hardness greater than that of the needle blanks) comprises particles having no curved surface feature with a radius of a size less than the diameter of the needle blank, which might be capable of producing a visible scratch The media may be substantially spherical. However, non-spherical media, e.g. stainless steel tapered pins, may also be employed. The medium is generally smooth. If the media is. rough, it should be softer than the blanks.
The particles of hard media are preferably spherical and have a diameter of from about 0.5 millimeters (mm) to about 10 mm, preferably about 2 mm to about 7 mm and a glassy smooth surface. The diameter varies with the size of the needle blank. For large (18-30 mil) wire diameters a spherical particle diameter of about 4 to about 8 mm is preferred. For small (down to 10 mil) wire diameters a spherical particle diameter of about 1 to about 3 mm is preferable. Hard media suitable for tumbling in the present invention include, for example, ceramic, porcelain, stainless steel and glass. Metallic media is generally used for larger needles in the 24 mil to 60 mil needle size range. Such metallic media could bend relatively smaller needles. Because of the extreme weight differences of standard metallic media relative to needles, glass or porcelain media is preferred. Porcelain is most preferred because it is generally more durable than glass. When abrasive media, such as rough surfaced aluminum oxide are employed for abrasive radiusing, it is advantage
Hail III Joseph J.
Shanley Daniel
United States Surgical Corporation
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