certain terminology may be used in the following description for convenience only and is not limiting . the words “ left ,” “ right ,” “ upper ,” and “ lower ” designate directions in the drawings to which reference is made . the words “ inwardly ” and “ outwardly ” refer to directions toward and away from , respectively , the geometric center of the needle and designated parts thereof . the terminology includes the words above specifically mentioned , derivatives thereof , and words of similar import . referring now to the drawings , and to fig1 in particular , an infusion set 10 in accordance with the present invention is shown temporarily positioned on an inserter assembly 12 for installation in the subcutaneous skin layer of a user . the infusion set 10 includes a cannula 14 extending from a generally hollow cannula housing 16 and an introducer needle 18 extending through the cannula 14 and into the cannula housing 16 . the cannula 14 is preferably constructed of a fluoropolymer material , such as teflon ™, or other inert material . an adhesive - backed pad 20 is preferably attached to the cannula housing 16 with the adhesive layer ( not shown ) facing away from the cannula housing 16 . a portion of the pad 20 is shown broken away in fig1 to more clearly illustrate the introducer needle 18 and cannula 14 extending underneath the housing . it will be understood that the infusion set 10 is not limited to the low - profile type , but may be arranged to insert the introducer needle 18 and cannula 14 at different angles , including perpendicular , to the skin surface . the inserter 12 includes an inserter housing 22 with an angled alignment guide 24 formed therewith so that the infusion set 10 can be inserted into the skin at a predetermined angle . the inserter 12 also includes a spring - loaded slide assembly 26 that is biased toward a forward position as shown , and is retractable to a rearward or cocked position . a locking mechanism 28 is adapted to hold the slide assembly 26 in the cocked position , and an actuating button 30 is operatively associated with the locking mechanism 28 for releasing the slide assembly 26 . a locking lever 32 can also be provided for preventing inadvertent depression of the actuating button 30 , and thus inadvertent release of the slide assembly 26 . further details of the inserter assembly can be found in copending u . s . patent application publication no . 2002 / 0077599 filed on dec . 18 , 2001 , the disclosure of which is hereby incorporated by reference . it will be understood that the infusion set 10 can be used with inserters of different configurations , or can be used without an inserter . with reference now to fig2 - 4 , the introducer needle 18 includes a body portion 40 and a tip portion 42 that is integrally formed with , and extends from , the body portion 40 . preferably , the body portion 40 and tip portion 42 are of solid construction . as shown , the body portion 40 is circular in cross section , but may be configured with other cross sectional shapes , such as triangular , square , oval , and so on . the tip portion 42 preferably includes a plurality of substantially planar wedge faces , such as first wedge face 46 , second wedge face 48 and third wedge face 50 that converge toward a common insertion point 52 from the body portion 40 . the common insertion point 52 is preferably coincident with a central axis 54 of the introducer needle 18 . preferably , the wedge faces extend from the solid body portion 40 to the central axis 54 at an angle a in the range of approximately 5 - 30 degrees , and more preferably at an angle a of approximately 15 degrees . as shown , the first and second wedge faces 46 and 48 intersect to form a first cutting edge 60 , the first and third wedge faces 46 and 50 intersect to form a second cutting edge 62 , and the second and third wedge faces 48 and 50 intersect to form a third cutting edge 64 . the cutting edges 60 , 62 and 64 preferably converge toward the common insertion point 52 from the solid body portion 40 and are preferably circumferentially spaced about the central axis 54 at an angle b of approximately 120 degrees . since the cutting edges extend along the intersection of the wedge faces , they also extend or slope from the solid body portion 40 to the common insertion point or central axis 54 at an angle a in the range of approximately 5 - 30 degrees , and more preferably at an angle a of approximately 15 degrees . in this manner , the length of each cutting edge 60 , 62 and 64 can be less than a cutting length of the prior art angle ground hollow needle to thereby reduce material costs . the introducer needle 18 is preferably constructed from a solid rod or bar of material , such as stainless steel , by cutting the rod or bar to a predetermined length , then grinding or otherwise forming one end of the rod or bar to form the tip portion 42 . referring again to fig1 in use , and by way of example , the infusion set 10 is loaded onto the slide assembly 26 of the inserter assembly 12 . the slide assembly 26 is then retracted to the cocked position and held in place by the locking mechanism 28 . the inserter assembly 12 is then positioned against the skin of a user and the button 30 is depressed to release the slide assembly 26 . the infusion set 10 moves together with the slide assembly under spring bias toward the skin until the introducer needle 18 and cannula 14 are positioned in the subcutaneous layer . the concentric location of the insertion point 52 together with the symmetrically spaced cutting edges 60 , 62 and 64 facilitate insertion of the introducer needle 18 into the skin with a concentric coaxial force . this coaxial force has no bending component , as in the prior art angle ground hollow needles . the three cutting edges 60 , 62 and 64 cooperate with the concentric insertion point 52 and the wedge faces 46 , 48 and 50 to minimize skin displacement during needle insertion while assuring a clean cut through the tissue . in addition , the solid construction of the introducer needle 18 gives added strength over prior art hollow body constructions . still another advantage of the above - described introducer needle 18 is less burr formation and easier burr removal during manufacturing than in the prior art angle grinding of hollow needles . still further , the introducer needle 18 facilitates assembly of the infusion set 10 . when inserted through the cannula 14 during assembly , the introducer needle 18 glides through without touching or damaging the cannula 14 since the insertion point 52 is spaced away from the wall of the cannula . referring now to fig5 a front elevational view of an introducer needle 18 a in accordance with a further embodiment of the invention is illustrated . the introducer needle 18 a has a tip portion 42 a with a plurality of substantially planar wedge faces , such as first wedge face 70 , second wedge face 72 , third wedge face 74 , and fourth wedge face 76 that converge toward a common insertion point 78 from the body portion 40 . the insertion point 78 is preferably coincident with a central axis of the introducer needle 18 a . preferably , the wedge faces extend from the solid body portion 40 to the central axis 78 at an angle a in the range of approximately 5 - 30 degrees , and more preferably at an angle a of approximately 15 degrees . as shown , the first and second wedge faces 70 and 72 intersect to form a first cutting edge 80 , the second and third wedge faces 72 and 74 intersect to form a second cutting edge 82 , the third and fourth wedge faces 74 and 76 intersect to form a third cutting edge 84 , and the fourth and first wedge faces 76 and 70 intersect to form a fourth cutting edge 86 . the cutting edges 80 - 86 preferably converge toward the insertion point 78 from the solid body portion 40 and are preferably circumferentially spaced about the central axis 54 at an angle c of approximately 90 degrees . since the cutting edges extend along the intersection of the wedge faces , they also extend or slope from the solid body portion 40 to the central axis 78 at an angle a that is preferably in the range of approximately 5 - 30 degrees , and more preferably at an angle a of approximately 15 degrees . while the two embodiments of the invention shown in fig4 and 5 illustrate inserter needles with 3 and 4 edge faces , it should be understood that the invention is not so limited and that 5 or more faces can be used . while the invention has been taught with specific reference to the above - described embodiments , those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the invention . by way of example , it will be understood that the invention is not limited to the particular number of wedge faces and cutting edges illustrated , but may have more or less faces and cutting edges . in addition , the angles between the cutting edges and / or their slopes can be asymmetrical . moreover , although the introducer needle has been taught for use with an inserter assembly , it will be understood that the introducer needle is not so limited , but may be used in other devices and / or methods for positioning a cannula or catheter in a membrane or tissue and / or for creating a passage or opening in a membrane or tissue . thus , the described embodiments are to be considered in all respects only as illustrative and not restrictive . the scope of the invention is , therefore , indicated by the appended claims rather than by the foregoing description . all changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope .
an introducer needle for an infusion set or the like includes a solid tip portion with a plurality of intersecting wedge surfaces that converge toward a common insertion point . preferably , the common insertion point is coincident with a central axis of the introducer needle . the tip portion also includes a plurality of cutting edges formed at intersections of the wedge surfaces . the cutting edges converge toward the common insertion point so that insertion of the introducer needle into the membrane causes even cutting and separation of the membrane around the introducer needle .