NEEDLE CANNULA WITH A GRINDED POINT

Abstract

The invention relates to a needle cannula having a proximal end, a distal end and a lumen there between. The needle cannula is provided with a sharp point formed in a three-facet grinding. The first ground facet is of elliptic shape and grinded symmetrically around a central axis, and the second and third ground facet are grinded substantially symmetrically on opposite sides of the first ground facet such that the second and third ground facet converge to form the distal needle tip. The length of each of the substantially identical second and third ground facet measured along the central axis is less than half, and preferably less than one third, of the length of the first ground facet measured along the central axis.

Claims

1. A needle cannula having a proximal end and a distal end and a lumen there between and wherein the distal end (3) is provided with a sharp point, the sharp point comprising: a first ground facet with a substantially elliptic shape grinded substantially symmetrically around a central axis (X), a second ground facet and a third ground facet grinded substantially symmetrically on opposite sides of the first ground facet and which second ground facet and third ground facet converge to form a distal needle tip, wherein, the length (b) of each of the second ground facet and of the third ground facet measured along the central axis (X) is less than half the length (a) of the first ground facet measured along the central axis (X).

2. The needle cannula according to claim 1, wherein the length (b) of each of the second ground facet and of the third ground facet measured along the central axis (X) is less than a third of the length (a) of the first ground facet measured along the central axis (X).

3. The needle cannula according to claim 1, wherein the length (a) of the first ground facet measured along the central axis (X) is in the range of 0.9 mm to 1.35 mm.

4. The needle cannula according to claim 1, wherein the length (b) of the second ground facet and of the third ground facet measured along the central axis (X) is in the range of 0.15 to 0.6 mm.

5. The needle cannula according to claim 1, wherein the distal end of the needle cannula is bended.

6. The needle cannula according to claim 5, wherein a bending area (d) of the distal end starting 0.1 mm to 0.2 mm proximally from the distal needle tip is bended.

7. The needle cannula according to claim 5, wherein the needle tip is bended to a position a radial distance (e) from the outer surface of the needle cannula.

8. The needle cannula according to claim 5, wherein the distal needle tip when bended lies within the clearance of the hollow lumen.

9. The needle cannula according to claim 5, wherein the distal needle tip when bended lies substantially on the central axis (X).

10. The needle cannula according to claim 1, wherein a planar surface following the first ground facet forms an angle α with the central axis (X) of the needle cannula and wherein the angle α is in the range of 10° to 15°.

11. The needle cannula according to claim 1, wherein the needle cannula is rotated an angle γ between grinding of the second ground facet and the third ground facet and wherein the angle γ is in the range of 120° to 160°.

12. The needle cannula according to claim 1, wherein the second ground facet and the third ground facet forms an angle β with the central axis (X) of the needle cannula and wherein the angle β is in the range of 25° to 35°.

13. The needle cannula according to claim 1, wherein the needle cannula is a G28, G29, G30, G31, G32, G33 or G34 needle.

14. The needle cannula with a distal sharp point according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

[0046] FIG. 1 show a side view of the needle cannula.

[0047] FIG. 2A show a top view of the needle cannula rotated 90° in relation to FIG. 1.

[0048] FIG. 2B show an enlarged section of the distal end of the needle cannula in FIG. 2A.

[0049] FIG. 3 show an end view of the needle cannula together with the grinding process.

[0050] FIG. 4 show an example of a hook formed at the sharp tip of a needle cannula.

[0051] FIG. 5 show a side view of the needle cannula being bended.

[0052] The figures are schematic and simplified for clarity, and they just show details, which are essential to the understanding of the invention, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts.

DETAILED DESCRIPTION OF EMBODIMENT

[0053] When in the following terms as “upper” and “lower”, “right” and “left”, “horizontal” and “vertical”, “clockwise” and “counter clockwise” or similar relative expressions are used, these only refer to the appended figures and not to an actual situation of use. The shown figures are schematic representations for which reason the configuration of the different structures as well as there relative dimensions are intended to serve illustrative purposes only.

[0054] In that context it may be convenient to define that the term “distal end” in the appended figures is meant to refer to the end of the needle cannula doing the actual penetration of the skin of a user, whereas the term “proximal end” is meant to refer to the opposite end. Distal and proximal is meant to be along an axial orientation extending along the central axis (X) of the needle cannula as also disclosed in FIG. 2A.

[0055] FIG. 1 discloses the needle cannula 1 which has a proximal end 2 and a distal end 3. The distal end 3 is the end that does the actual penetration of the skin of a user during injection. A hollow lumen 4 provides the flow way for the liquid drug to be injected.

[0056] The needle cannula 1 is preferably secured in a needle hub as e.g. shown in WO 2002/076540. In such example, the proximal end 2 of the needle cannula 1 penetrates through a septum in a cartridge when the injection needle is connected to an injection device.

[0057] The distal end 3 of the needle cannula 1 is grinded in a 3-facet grind. During grinding the individual needle cannula 1 is held in a fixture and the distal end 3 is grinded in a first ground facet 5. This first ground facet 5 has an elliptic shape and is substantially symmetrically placed around the central axis X as disclosed in FIG. 2A.

[0058] The angle α appearing between a planar surface following the first ground facet 5 and the central axis X is preferably between 11° to 14° and most preferably 12.5°+/−1°. The length of the first ground facet 5 is indicated as “a” in FIG. 2B and is preferably 0.9 mm to 1.35 mm and most preferably 1.125+/−0.2 mm.

[0059] The proximal end 2 of the needle cannula 1 is grinded in a 1-facet grind. The angle c used for the grinding at the proximal end is preferably 20° to 36° and most preferably 28°+/−4°. When the needle cannula 1 is used for a pen needle, the grinding at the proximal needs only to be sufficient for the proximal end 2 to penetrate through the septum of the cartridge containing the liquid drug. However any kind a grinding can eb applied to the proximal end 2 of the needle cannula 1.

[0060] Following the grinding of the first ground facet 5, the individual needle cannula 1 is rotated around the central axis X as disclosed in FIG. 3 in order have the two sides of the first ground facet 5 grinded. The needle cannula 1 is first rotated in one rotational direction and thereafter in the opposite rotational direction. The total angle γ of rotation is 140+/−10. When rotated each side of the first ground facet 5 is grinded in a second ground surface 10 and a third ground facet 15 as illustrated in FIG. 2A-B. These two ground facets 10, 15 are grinded substantially symmetrically around the central axis X and converge into a distal needle tip 11 at the most distal end 3 of the needle cannula 1.

[0061] When the needle cannula 1 has been rotated approximately 70° to each rotational side, the second ground facet 10 and the third ground facet 15 are grinded at an angle β being between 25° to 35° and most preferably 30°+/−3°.

[0062] The axial length of the second ground facet 10 and the third ground facet 15 is indicated as “b” in FIG. 2B and is preferably less than half of the length “a” of the first ground facet 5. More preferably the length b is less than a third of the length a of the first ground facet 5. The ratio between “b” and “a” should henceforth be less than 0.5 and preferably less than 0.33. In numbers the preferred length of b is 0.196 to 0.56 mm.

[0063] FIG. 4 shows an example of a hook 12 formed at the distal needle tip 11 of a needle cannula 1. If the distal needle tip 11 is exposed to an axial force, the distal needle tip 11 will curl and form a hook 12 pointing away from centre axis (X) of the needle cannula 1. Such hook 12 would have the shape of a fishing hook. When the user then retracts the distal needle tip 11 from the skin this hook 12 will cause extra damage to the tissue and obviously also provide a less comfortable feeling.

[0064] For many injection needles commercially available it can be measured that such hook 12 is formed when the axial force on the distal needle tip 11 is higher than approximately 1 to 2 newton. However, experiments have demonstrated that if the length of the second ground facet 10 and the third ground facet 15 is made sufficiently short the force needed to form a hook 12 will increase dramatically.

Examples of the Invention

[0065] Two identical G30 needle cannulae 1 have been grinded in a three-facet grind with the following dimensions;

Example 1

[0066] α=12.8°+/−1°
β=30°+/−3°
γ=140°+/−10°
a=1.125 mm+/−0.15 mm
b=0.41 mm+/−0.15 mm
b/a=0.36
Hook resistance=8 Newton

Example 2

[0067] α=12.5°+/−1°
β=30°+/−3°
γ=140°+/−10°
a=1.125 mm+/−0.15 mm
b=0.296 mm+/−0.1 mm
b/a=0.26
Hook resistance=12 Newton

[0068] Following the grinding of the three-facet grinds, the force required to form a hook 12 was measured. In the first example, a hook 12 was formed when the force reached 8 Newton, and in the second example, the force required to form a hook was 12 Newton.

[0069] In both examples, the force needed to form a hook at the distal needle tip 11 was substantially higher than in the commercially available needle cannulae. The needle cannulae 1 according to the invention were thus more hook resistant when compared to commercially available needle cannulae.

[0070] FIG. 5 show an example wherein the distal needle tip 11 has been bended inwards toward the centre axis X. As seen in FIG. 5, the distal end 3 is provided with a bending area “d” which is located a proximal distance “c” from the distal needle tip 11.

[0071] In a preferred embodiment, the bending area “d” has a length on 0.55 mm+/−0.5 mm and is stretching in the proximal direction from a distance c of 0.15 mm+/−0.05 mm from the distal needle tip 11.

[0072] The actual bending of the distal end 3 is made by bending the bending area “d” without actively bending the outer distal distance “c”. The outer contour of the needle cannula 1 prior to bending is indicated in FIG. 5.

[0073] The distal needle tip 11 is preferably bended to a position in a radial distance “e” from the outer surface of the needle cannula 1. This radial distance “e” is preferably such that the distal needle tip 11 lies within the clearance of the lumen 4 of the needle cannula 1. Most preferably is the distal needle tip 11 bended to a position wherein it follows the central axis X of the needle cannula 1 as disclosed in FIG. 5. The distance e would thus be half the outer diameter of the needle cannula 1.

[0074] In one example the needle cannula 1 could be a G30 cannula with an outer diameter on 0.31 mm+/−0.01 mm and an inner diameter on 0,175 mm+/−0.01 mm and wherein “e” is 0,155 mm+/−0.1 mm.

[0075] When the distal needle tip 11 of a needle cannula 1 without bending is exposed to an axial force and forms a hook 12, this hook 12 will point in a direction outwardly from the outer surface of the needle cannula 1 and away from the lumen 4 as disclosed in FIG. 4. However, when the needle cannula 1 is bended at the distal end 3, as suggested herein, the hook 12 will form to the opposite side, i.e. towards the central axis X and the opposite surface of the needle cannula 1 as indicated by the arrow H in FIG. 4. Once the hook 12 lies within the contour of the needle cannula 1 it becomes more comforting for the user to remove the needle cannula 1 from the skin as the damage to the tissue and the following pain is greatly reduced.

[0076] Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject matter defined in the following claims.