Patent Description:
A medication pen for delivering self-administered medications generally includes a pen body, which houses a medication compartment, and a separate pen needle which may be attached to and detached from the pen body. The pen needle includes a needle hub having a recess on the proximal side for receiving the pen body and a proximal (non-patient end) needle accessing the medication compartment, typically piercing the septum of a medication cartridge in the pen body. The distal patient end of the pen needle includes the needle or cannula that is inserted into the injection site.

Injections may be performed in the intradermal (ID) region, the subcutaneous (SC) region and the intramuscular (IM) region. For many types of injectable medications, including insulin, the SC region is preferred for administering an injection. See, for example, <NPL>).

Shorter needles, such as <NUM> and <NUM> needles, are adapted to achieve injection to a specified target depth in a subcutaneous region. In one aspect, the present invention addresses the need to ensure that a needle is inserted to its target depth, regardless of the angle at which the user may approach the injection site with the medication pen.

In certain prior art pen needles the cannula is supported in an axially positioned post on the needle hub. The post forms a narrow portion extending distally from the relatively wider portion in which the pen body is received. In other pen needles known in the art, a distal face of the needle hub placed against the injection site may have a slight taper at the edge. However, the edge of the needle hub engages the skin when the cannula is inserted at an angle, interfering with the injection. The slight taper is not functional during an injection, or is only at the edge of the distal face of the needle hub, generally having a radius of curvature greater than about <NUM>. Example devices of the prior art are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

While the prior devices are generally suitable for the intended use, there is a continuing need for improved devices for controlling the penetration of a cannula for delivering a drug or medicament.

The present invention is directed to a needle hub assembly for coupling to an injection pen where the needle hub has a skin contact surface configured for controlling the depth of penetration by a cannula extending from the needle hub. The needle hub has a contact surface with a height and width that complement each other to control the depth of penetration of the cannula.

These and other objects of the invention are achieved in one aspect of the invention by a pen needle assembly having a needle hub with a cannula, an inner shield for covering the cannula and an outer cover that fits over the inner shield and the needle hub.

One feature of the invention is to provide a pen needle hub assembly having a needle hub with a cannula, an inner shield that fits over a top portion of the needle hub to enclose the cannula and an outer cover that fits over the inner shield and needle hub, with a peel tab for closing the open end of the outer cover. The needle hub in one embodiment has a body with a side wall with a top end and a bottom end. The top end of the side wall has an outer surface with a plurality of recesses extending in a longitudinal direction with respect to a central axis of the needle hub, where the recesses form a scalloped shape. The recesses can result in the top end of the side wall with greater flexibility compared to the side wall where no recesses are formed. The recesses cooperate with the outer cover to rotate the needle hub when coupling to and removing from the pen delivery device.

The bottom end of the side wall of the needle hub can have an inner surface with at least one recessed portion so that the bottom end of the wall has a thickness to provide some flexibility similar to or complementing the flexibility of the top end of the side wall. In one embodiment, the recess on the inner surface of the bottom end of the side wall can be continuous and extend around the entire circumference of the side wall at the open end of the needle hub and provide an opening with a dimension to allow easy coupling of the needle hub to the pen needle device.

Another feature of the invention is to provide a needle hub having a body with a side wall, a top surface forming a shoulder extending perpendicular to the central axis of the needle hub, and a tower or upper portion extending upwardly from the top surface a distance to from a contact surface with the skin of the patient during injection. The tower has an end wall with an axial face at a distal end forming the skin contact surface. A supporting post extends inwardly from an inner face of the end wall with a central channel or bore to receive the cannula. The post projects axially into the cavity of the hub a distance to support the cannula. In one embodiment, the inner surface of the end wall has at least one, and typically a plurality of reinforcing ribs, that extend radially between the post and a side wall of the tower.

The inner shield of the invention can have a dimension to fit over the tower of the needle hub to enclose a top portion of the needle hub and enclose the cannula. The inner shield has a body with a side wall having an inner dimension to fit over the tower of the needle hub. An outwardly extending flange extends from a bottom end of the inner shield to contact the top wall of the body of the needle hub to limit the depth of insertion of the needle hub into the inner shield. The flange can have an outer dimension to complement the outer dimension of the body of the needle hub.

In one embodiment of the invention the inner shield has an upper portion extending from the body of the inner shield a distance to enclose the cannula. The outer surface of the inner shield can be provided with one or more griping members projecting outwardly from the side of the upper portion. In one embodiment, the gripping members can be a projecting member with a surface that is inclined with respect to the center axis of the inner shield.

The outer cover of the invention can have a dimension to enclose the inner shield and the needle hub. The inner shield can have a body with a side wall defining an open end of the outer cover. A bottom end of the side wall next to or adjacent the open end has an outwardly extending flange that surrounds the perimeter of the side wall. An inner surface of the side wall has a recess at the open end to provide a space or gap between the inner surface of the outer cover and the needle hub. The bottom end of the side wall can have a beveled or chamfered inner edge.

According to the invention, the inner surface of the body of the outer cover has at least one and typically a plurality of radially spaced detents extending into the cavity of the body of the outer cover. The detents can extend in a longitudinal direction with respect the center axis of the outer cover and project inwardly to provide a friction fit of the outer cover to the outer surface of the needle hub. The outer surface of the outer cover has a plurality of recesses that form the detents on the inner surface. One or more stop members are formed on the inner surface of the body of the outer cover and provided with a downwardly oriented face for engaging the top end of the needle hub or the inner shield to limit the travel of the needle hub and inner shield into the cavity of the outer cover. The stop members are formed with one or more of the detents and include a portion extending radially inward a distance to engage the flange on the inner shield.

The needle hub in various embodiments of the invention can have a convex distal axial surface for contacting the skin during needle insertion and drug delivery. The needle hub can have a contact surface area of about <NUM>-<NUM><NUM>. The contact surface in one embodiment can have a height of about of <NUM> to <NUM> and a surface area of <NUM>-<NUM><NUM>.

The needle hub can have a convex surface with a height of about <NUM> to <NUM> and a cannula with a length of about <NUM>-<NUM> projecting from the contact surface for penetrating the skin. The cannula can be located in the center of the contact surface so that the contact surface surrounds the cannula. In one embodiment the invention, the convex contact surface can have a height of about <NUM> to <NUM> and width of about <NUM> to <NUM> to provide sufficient surface area and a suitable shape and angle with respect to the axis of the cannula to contact the skin and provide the controlled depth of penetration by the cannula into the skin. In one embodiment, the cannula can have a length of about <NUM>.

It will be understood that each of the preferred or optional features of the various embodiments may be combined with other features and features described in combination with one or more particular features may also be combined with one or more other features of the other embodiments.

These and other features of the invention will become apparent from the following detailed description of the invention, which in conjunction with the drawings disclose various embodiments of the invention.

The following is a brief description of the drawing in which:.

A "medication pen" is used herein to refer to a device having a medication compartment, typically containing multiple doses of medication, and a separate pen needle. The phrase "pen needle" refers to a needle-bearing assembly which can be attached to the medication pen body so that a proximal end of the pen needle assembly accesses a medication compartment and a distal end is adapted for insertion into an injection site to perform one or more injections. The terms "needle" and "cannula" are used herein interchangeably to refer to a thin tubular member having a beveled end for insertion into an injection site on a subject. As used herein, the "distal" direction is in the direction toward the injection site, and the "proximal" direction is the opposite direction. "Axial" means along or parallel to the longitudinal axis of the needle and the "radial" direction is a direction perpendicular to the axial direction.

The invention is directed to an injection device and particularly to a needle hub assembly having a cannula with a predetermined length for penetrating the skin to a predetermined penetrating depth. The injection device has a skin contact surface for contacting and deforming the skin when the cannula penetrates the skin to assist in controlling the depth of penetration at various angles of injection with respect to the surface of the skin. The contact surface has a predetermined shape, width and height to control the depth of penetration into the skin to the desired layer of the skin.

The skin contact surface of the pen needle device surrounding the cannula has a width and height configured for providing greater control of the depth of penetration by the cannula. In one embodiment of the invention, the pen needle device is configured to obtain a cannula penetration of about <NUM>. The skin contact surface is further configured to control the shape, width and depth of deformation of the skin surface when the device is pressed against the skin during the penetration of the cannula. The width is determined as being the surface area that contacts the skin during the insertion of the cannula and during the injection or delivery of the drug using a normal insertion force. The height refers to the linear distance between the outer peripheral edge of the contact surface and the proximal end of the contact surface.

The injection device includes drug delivery device such as a pen needle device having an outer sleeve, a medicament cartridge sealed by a septum and a cap. A plunger is provided on the end of the cartridge to dispense the drug. The delivery pen has a structure and operation similar to those known in the art. A pen needle hub <NUM> is coupled to the injection device for delivering the drug to the patient. The pen needle hub <NUM> according to one embodiment of the invention shown in <FIG> includes an outer cover <NUM>, an inner shield <NUM>, a needle hub <NUM> and a tear drop shaped tab <NUM> attached to the outer cover <NUM> to provide a sterile seal. The needle hub <NUM> includes a double-ended cannula <NUM> beveled and sharpened at both ends for coupling to the pen needle assembly and for penetrating the skin of the patient.

In the embodiment of <FIG>, the needle hub <NUM> for coupling to the delivery pen has a body <NUM> having a side wall <NUM> to form an open end <NUM>. In the embodiment shown, body <NUM> has a substantially cylindrical shape. The open end <NUM> forms an internal cavity with internal threads <NUM> as shown in <FIG> and <FIG> for coupling to the pen needle delivery device. In another embodiment, the needle hub may be provided with flattened sides to assist in rotating the needle hub and coupling the needle hub to the pen needle assembly.

Body <NUM> of needle hub <NUM> has a distal end with a peripheral edge <NUM> forming a shoulder <NUM>. The shoulder can be oriented in a plane substantially perpendicular to a central axis of the needle hub <NUM>. A tower <NUM> forming an upper end portion of needle hub <NUM> extends from shoulder <NUM> in the direction of the central axis away from the open end <NUM>. The tower <NUM> has a side wall <NUM> extending substantially parallel to side wall <NUM> of body <NUM> of needle hub <NUM>. Tower <NUM> has an end wall <NUM> with a distal, axial face <NUM> forming a skin contact surface. End wall <NUM> can have a substantially convex shape. Axial face <NUM> can have a diameter of about <NUM> to <NUM>. The shoulder has a width to receive the inner shield and a width of about <NUM>-<NUM> from the peripheral edge of body <NUM> and side wall <NUM> of tower <NUM>.

A post <NUM> for supporting a cannula extends inwardly from an inner face <NUM> of end wall <NUM> of tower <NUM> as shown in <FIG>. Post <NUM> projects inwardly in the direction of the center axis for supporting cannula <NUM>. Post <NUM> has an axial passage extending through needle hub <NUM> for receiving the cannula and a conical shaped end <NUM>. A well <NUM> is formed in end wall <NUM> at the distal face <NUM> for receiving an adhesive to couple cannula <NUM> to needle hub <NUM>. In the embodiment shown, cannula <NUM> extends inwardly a distance for connecting the delivery device and extends outwardly from distal face <NUM> a distance for piecing the skin of the patient.

The needle hub <NUM> of <FIG> deforms the skin by the insertion force during the insertion and penetration of the cannula by an insertion force normally applied by the patient. In the embodiment shown, the needle hub <NUM> has an inner ring <NUM> extending from the distal face <NUM> of tower <NUM>. Inner ring <NUM> has an axially facing distal face <NUM> surrounding well <NUM> and cannula <NUM> with an inner side surface <NUM>. An outer ring <NUM> is formed at the outer peripheral edge of tower <NUM> forming a recess <NUM> between inner ring <NUM> and outer ring <NUM>. Outer ring <NUM> has an axially facing distal face <NUM> with an inner surface <NUM> facing inner side surface <NUM>. In the embodiment shown, the surface of recess <NUM> and the axial faces of inner ring <NUM> and outer ring <NUM> have a substantially continuous, concentric radius of curvature and define the skin contact surface of needle hub <NUM>. Recess <NUM> has a depth so that the skin of the patient deflects into the recess and contacts the bottom surface of the recess during needle insertion to deform the skin in a controlled manner. In one embodiment, the radial width of recess is substantially equal to the combined radial width of inner ring <NUM> and outer ring <NUM>. The axial surface of the distal face of tower <NUM> has a convex dome shape where inner ring <NUM> is spaced axially outward relative to outer ring <NUM> and the axially facing surface of recess <NUM>.

The initial penetration of the cannula <NUM> by the contact of the inner ring projecting from the tower <NUM> with the skin of the patient forms a depression in the skin and an initial cannula penetration depth. The surface of the skin then relaxes so that the surface of the skin conforms substantially to the shape of the contact surface formed by outer ring <NUM> and recess <NUM> and limits the depth of penetration of the cannula <NUM>. The shape, surface area and height of the contact surface to provide control of the depth of penetration of the cannula during the insertion and penetration force being applied to the injection device.

Referring to <FIG>, side wall <NUM> of body <NUM> has an inner surface <NUM> at the proximal open end <NUM> of needle hub <NUM>. In the embodiment shown, a recess <NUM> is formed in the inner surface <NUM>. In one embodiment, recess <NUM> surrounds the circumference of needle hub <NUM> to form a continuous recess. Recess <NUM> extends a distance of side wall and terminates at an inclined beveled edge <NUM>. Recess <NUM> can provide a larger open end to assist in assembling needle hub <NUM> to a delivery device.

As shown in <FIG> an outer surface <NUM> of side wall <NUM> includes a plurality of recesses <NUM> at the upper end forming a scalloped shape. Each recess <NUM> has a longitudinal length to cooperate with the outer cover <NUM> to assisting in rotating needle hub <NUM> and coupling to the pen needle assembly or other delivery device. Each recess <NUM> has a substantially V-shape formed by inclined sides <NUM> and an open top end <NUM>. The recess <NUM> can provide the upper portion of the side wall with increased flexibility relative to a surface without recesses. Recess <NUM> in the bottom end of the side can provide a reduced thickness and flexibility similar to the flexibility provided by the recesses <NUM>.

Referring to <FIG>, inner face <NUM> of end wall <NUM> has a substantially conical shape corresponding to the shape of outer distal face <NUM>. In the embodiment shown, end wall <NUM> has a substantially uniform thickness. Radially extending ribs <NUM> can be formed on inner face <NUM> of end wall <NUM> as shown in <FIG>. <FIG> is a bottom view showing ribs <NUM> extending between post <NUM> and an inner surface of side wall <NUM>. For clarity, cannula <NUM> is not shown in <FIG> althought it is understood that hub <NUM> will include cannula <NUM> during use. Post <NUM> has a conical shaped base portion <NUM> at the inner face <NUM> that converges to the cylindrical surface of post <NUM>. In one embodiment, ribs <NUM> extend along the outer face of the conical portion <NUM> and the inner face <NUM>. Ribs <NUM> have a width and axial height to increase the strength of end wall <NUM> and inhibit or reduce bending and deflection of end wall <NUM> during use.

During penetration of cannula <NUM>, end wall <NUM> of tower <NUM> contacts the skin of the patient. Ribs <NUM> on inner surface <NUM> provide sufficient strength to end wall <NUM> to resist deflection and deforming of end wall <NUM> inwardly into the cavity and resist collapsing of the conical shape of end wall <NUM> when an excess insertion force is applied to the end wall <NUM>. Ribs <NUM> also provide sufficient strength so that end wall <NUM> is sufficiently rigid to prevent an outward deflection or distortion of end wall <NUM> when a pulling force is applied that may cause failure of the adhesive and provide a predetermined pull force for removal of cannula. In the embodiment shown, four ribs <NUM> are provided although the number of ribs can vary depending on the stiffness of the end wall <NUM>. The conical base <NUM> also provides stiffness to the end wall <NUM> to resist deflecting inward during use.

Referring to <FIG>, inner shield <NUM> has a length to receive cannula <NUM> and a width to cooperate with needle hub <NUM>. Inner shield <NUM> as shown has a body <NUM> forming an end portion, a side wall <NUM> and a flange <NUM> extending radially outward from side wall <NUM> of body <NUM>. Body <NUM> has a shape and an inner dimension complementing an outer shape and dimension of tower <NUM> of needle hub <NUM>. Side wall <NUM> of body <NUM> has an inner surface for mating with the outer surface of side wall of tower <NUM>. Internal ribs <NUM> extending in a longitudinal direction are formed on the inner surface of side wall <NUM> for gripping with the outer surface of tower <NUM> to provide a friction fit. Ribs <NUM> allow air to escape from the cavity of inner shield during assembly and disassembly to enable a controlled insertion and pull force with respect to needle hub <NUM>. As shown in <FIG>, an upper distal end of ribs <NUM> have an inwardly extending lip <NUM> to contact the shoulder <NUM> of needle hub <NUM> to limit insertion depth of needle hub <NUM> into inner shield <NUM>. Flange <NUM> is oriented to mate with the shoulder <NUM> of body <NUM> as shown in <FIG>. In the embodiment shown, flange <NUM> extends in a plane substantially perpendicular to a central axis of inner shield <NUM> and has a dimension defined by a peripheral edge <NUM> complementing the outer dimension of shoulder <NUM> and an outer dimension of side wall <NUM> of body <NUM> of needle hub <NUM>.

Inner shield <NUM> includes a top wall <NUM> with a substantially concave outer surface and a conical shaped top end portion <NUM> extending axially from top wall <NUM> of body <NUM> with an internal dimension to receive cannula <NUM> when inner shield is coupled to needle hub <NUM> as shown in <FIG>. Top end portion <NUM> in the embodiment shown, is defined by inclined side walls <NUM> that converge toward a distal end <NUM>. Each wall has a slight convex curvature with a textured or gripping surface. In the embodiment shown, four walls are included to form a substantially square cross section. As shown in <FIG>, side walls <NUM> have a width that decreases from body <NUM> to distal end <NUM>. In other embodiments, top end portion <NUM> can have a rounded, cylindrical shape or tapered conical shape. Inclined side walls <NUM> have a gripping surface for assisting in the user gripping and removing inner shield <NUM> from needle hub <NUM> and placing inner shield back onto needle hub <NUM> after use. The gripping surface can be a roughened or textured surface portion or projecting members to assist in gripping and rotating inner shield <NUM> relative to needle hub <NUM>.

In the embodiment shown, side walls <NUM> are formed with at least one, and typically a plurality of grips <NUM> spaced along the longitudinal length of each side wall <NUM>. Grips <NUM> can be positioned at the distal end of the inner shield or spaced along the length of the inner shield. Grips <NUM> extend outwardly to allow the user to easily grip and rotate the inner shield when removing the inner shield from the needle hub <NUM>. In the embodiment shown three grips <NUM> are provided on each side wall <NUM>. In other embodiments, more than three or fewer than three grips can be provided. Grips <NUM> in the embodiment shown have an inclined major face <NUM> and an inclined minor face <NUM>. Major face <NUM> is inclined outwardly toward distal end <NUM> and has a surface area sufficient to be gripped by the user. Minor face <NUM> is inclined toward body <NUM> of inner shield <NUM>. As shown in <FIG>, grips <NUM> have a decreasing width with the decreasing width of each side wall toward distal end <NUM>.

Outer cover <NUM> has a shape and dimension to complement the shape and dimension of inner shield <NUM> and needle hub <NUM>. Outer cover <NUM> has a body <NUM> with a side wall <NUM>, a bottom end forming an open end <NUM> for receiving inner shield <NUM> and needle hub <NUM>. A flange <NUM> extends radially outward from the bottom end. Flange <NUM> is oriented to mate with flange <NUM> of inner shield <NUM> and shoulder <NUM> of needle hub <NUM>. In the embodiment shown, flange <NUM> has a peripheral edge <NUM> defining a radial dimension complementing the outer dimension of needle hub <NUM>. The open end of outer cover <NUM> includes a beveled or chamfered edge <NUM> extending from a bottom face of flange <NUM> to the inner surface of side wall <NUM>.

Side wall <NUM> of body <NUM> terminates at a top end <NUM> and converges inwardly to form a conical shaped axial face <NUM>. A top section <NUM> forming a top end having a side wall <NUM> extends from conical shaped face <NUM> to a distal end <NUM>. A plurality of ribs <NUM> extend radially outwardly in a longitudinal direction from an outer surface of side wall <NUM>. An inner surface <NUM> of side wall <NUM> includes indicia, such as at least one and typically a plurality of ribs <NUM>. Ribs <NUM> can be provided to resist crushing or deflection of outer cover <NUM> during removal and assembly. In the embodiment shown, ribs <NUM> extend around the inner surface <NUM> and are oriented substantially perpendicular to the longitudinal axis of outer cover <NUM>. Three ribs <NUM> are shown aligned and spaced apart around the inner surface to provide strength to the side wall <NUM> during use.

In one embodiment, ribs <NUM> provide indicia to define a predetermined volume in the end of the outer cover <NUM>. During use, the pen needle can be actuated to deliver a medication into the outer cover to measure the dosage delivered by the pen needle using the ribs as indicia to measure the volume and accuracy of the delivery device. In other embodiments, other forms of indicia can be used to mark a predetermined volume in the outer cover.

Referring to <FIG>, side wall of <NUM> of body <NUM> includes at least one and typically a plurality of detents <NUM> extending from an inner surface <NUM> in a longitudinal direction with respect to the center axis of outer cover <NUM>. Detents <NUM> are oriented to mate with recesses <NUM> of needle hub <NUM> during assembly to enable rotating of needle hub <NUM> by rotation of outer cover <NUM> during coupling and removing needle hub <NUM> from a pen delivery device. The inclined sides <NUM> of the respective recess <NUM> provide an enlarged open end of the recess to receive the detents <NUM>. In the embodiment shown in <FIG>, eight detents <NUM> are provided, while in other embodiments four detents are provided.

Detents <NUM> are formed by molding recesses <NUM> on an outer face <NUM> of side wall <NUM>. As shown in <FIG>, recesses <NUM> extend in a longitudinal direction at a top end of side wall <NUM> and form an open end in the conical face <NUM>. Detents <NUM> have a length to mate with the recesses <NUM> while allowing needle hub <NUM> to be received in outer cover <NUM> as shown in <FIG> so that a bottom edge of needle hub <NUM> is recessed within the cavity of outer cover <NUM>. In one embodiment, one or more of the detents have an inclined end to assist in guiding the detents into the respective recess <NUM>. In the embodiment shown, alternating detents <NUM> have a longer length than the adjacent detents to engage the corresponding recess <NUM> in needle hub <NUM> to align all of the detents with a respective recess by positioning outer cover <NUM> on needle hub <NUM>. The longer detents having an end closer to the bottom edge of needle hub <NUM> than the adjacent detents have an inclined or angled end face forming a point to pass easily into the recess <NUM>.

As shown in <FIG> at least one stop member <NUM> is formed on the inner face <NUM> to limit the depth of inner shield <NUM> and needle hub <NUM> into the cavity of outer cover <NUM>. Stop member <NUM> is formed at an upper end of side wall <NUM> and has a downwardly facing surface <NUM> positioned to contact a top face of flange <NUM> of inner shield <NUM> or a top face of shoulder <NUM> of needle hub <NUM>. Stop member <NUM> can be formed with one or more detents <NUM> as shown in <FIG>. In the embodiment shown, four detents are provided and spaced radially around the inner surface of the side wall <NUM> a substantially uniform distance.

The needle hub assembly <NUM> of the invention is assembled in the manner shown in <FIG>. Inner shield <NUM> is positioned on the top end of needle hub <NUM> where flange <NUM> of inner shield <NUM> contacts shoulder <NUM> of needle hub <NUM>. Outer cover <NUM> is then placed over inner shield <NUM> and needle hub <NUM> where stop member <NUM> contacts the top face of flange <NUM> of inner shield <NUM> to capture inner shield between needle hub <NUM> and outer cover <NUM>. Detents <NUM> on outer cover <NUM> mate with the recesses <NUM>. In the embodiment shown, needle hub <NUM> is recessed slightly from the bottom face of flange <NUM> and the chamfered edge <NUM>. The detents <NUM> contact the outer surface of side wall <NUM> of needle hub <NUM> to form an annular gap or recess <NUM> between outer cover <NUM> and needle hub <NUM>.

Tab <NUM> is attached to the open end of outer cover <NUM> to seal the assembly. In one embodiment of the invention, tab <NUM> has a substantially tear drop shape to assist the user in removing the tab <NUM> from the outer cover to expose the needle hub <NUM>. Tab <NUM> can include a thermoplastic film for heat sealing to the open end of outer cover <NUM>. The thermoplastic film has a thickness to ensure complete sealing of outer cover <NUM> to provide a sterile seal. The thermoplastic film can have a thickness such that a portion of the thermoplastic under the sealing and bonding pressure may flow outwardly or inwardly from the bottom face of the flange <NUM>. The recess <NUM> formed between the needle hub <NUM> and outer cover <NUM> and the recess formed by the chamfered edge <NUM> can receive the excess flow of thermoplastic material to prevent the thermoplastic material from contacting needle hub <NUM> and prevent interference with the removal of needle hub <NUM> from outer cover <NUM>.

The skin contact surface formed by the distal face <NUM> has a substantially convex or conical shape forming a continuous and uniform curvature extending from the outer edge of tower <NUM> of needle hub <NUM> to the distal end or outermost portion of the contact surface of the needle hub and the cannula <NUM> so that the skin contact surface has a substantially semispherical or dome shape that contacts the skin during penetration of the cannula and delivery of the drug. The convex surface of the skin contact area can have a width or diameter of greater than <NUM> and typically about <NUM> to <NUM> and a height of about <NUM> to about <NUM> measured from the outer peripheral edge of the contact surface to the outermost center portion of the contact surface surrounding the cannula and spaced axially from the peripheral edge. In one embodiment the convex skin contact surface has a height of about <NUM> and a diameter of about <NUM>. The convex surface can have a radius of curvature of <NUM> to <NUM>. In various embodiments of the invention, the convex surface has radius of curvature of <NUM> to <NUM>. In other embodiments, the convex surface can have a radius of curvature of <NUM> to <NUM>. In one embodiment, the convex contact surface has a radius of curvature equal to or greater than the diameter of the contact surface. The radius curvature can be about <NUM> to <NUM><NUM>/<NUM> times the diameter of the contact surface.

The ratio of the diameter (D) to the height (H) of the contact surface influences the depth of penetration of the cannula on insertion into the skin. Generally, the larger the ratio provides more surface area that will contact the skin and greater control of the depth of penetration. A smaller ratio D:H provides a smaller surface area that can compress the skin on insertion and result in a deeper penetration of the cannula. In certain embodiments, the ratio of the diameter to the height of the surface area can range from about <NUM>:<NUM> to <NUM>:<NUM>. In other embodiments the ratio can range from about <NUM>:<NUM> to <NUM>:<NUM>.

Claim 1:
A pen needle assembly comprising:
a needle hub (<NUM>) having an open end for coupling with a delivery pen for delivering a medication, a distal end opposite said open end, and a cannula (<NUM>) extending from said distal end;
an inner shield (<NUM>) having a body (<NUM>) with an open end for coupling to said needle hub (<NUM>), and having a radially extending flange at said open end; and
an outer cover (<NUM>) having a body (<NUM>) with an open end for coupling to the needle hub (<NUM>), an upper section extending from said body (<NUM>) of said outer cover (<NUM>)
characterized by
the outer cover (<NUM>) further having an outer surface with an external gripping surface, and an inner surface, a plurality of detents (<NUM>) projecting inwardly from an inner surface (<NUM>) of said body of said outer cover and oriented for contacting an outer surface of said needle hub, and a stop member (<NUM>) projecting from a respective detent and oriented to contact a top surface of said flange to capture said flange of said inner shield (<NUM>) between an axially facing surface of said needle hub (<NUM>) and said stop member.