Needle for penetrating a membrane

1. A membrane penetrating needle for repeatedly penetrating a membrane, having a pointed end provided with a blunt penetrating tip and with an opening for letting a liquid in and/or out in a main direction which is substantially parallel to the longitudinal extension of the needle, wherein the blunt penetrating tip is designed with a rounded point to initially prick a membrane when the membrane is penetrated and that the outer edges present on the pointed end in the area from the rounded point to a position beyond the opening are rounded so that after the initial penetration the pointed end will push the membrane material away rather than cutting the membrane material; wherein the rounded point is arranged to lie substantially on a longitudinal centre line of the needle when viewed along the longitudinal centre line of the needle, and wherein the cross section of the penetrating tip of said membrane penetrating needle is substantially triangular with rounded corners and has a symmetry causing at least three substantially equally sized forces (F) in different directions which are radial to the longitudinal centre line of the needle and which forces counteract each other so that the needle will tend not to deviate from the initial penetration direction when the needle penetrates a membrane.

2. A membrane penetrating needle according to claim 1 , wherein the inner edge of the opening is rounded.

3. A membrane penetrating needle according to claim 1 , wherein the cross section of the proximal end of the needle is substantially circular.

4. A membrane penetrating needle according to claim 1 , wherein the pointed end has a shape substantially corresponding to a part of an imaginary cone, the tip of which coincides with the rounded point.

5. A membrane penetrating needle according to claim 1 , wherein the opening is arranged on one and the same half of a cross section of the needle.

6. A membrane penetrating needle according to claim 1 , wherein the pointed end is provided with a basic shape in accordance with a lancet bevel cut.

7. A membrane penetrating needle according to claim 1 , wherein the pointed end is provided with a basic shape in accordance with a back bevel cut.

8. A membrane penetrating needle according to claim 7 , wherein the back bevel cut has a tip angle (α) in the interval 20° to 50°.

9. A membrane penetrating needle according to claim 7 , wherein the back bevel cut has a tip angle (α) in the interval 50° to 100°.

10. A membrane penetrating needle according to claim 7 , wherein the back bevel cut has a tip angle (α) in the interval 30° to 80°.

11. A membrane penetrating needle according to claim 10 , wherein the tip angle (α) is approximately 75°.

12. A membrane penetrating needle according to claim 7 , wherein the back bevel cut has a second grind angle (β) in the interval 50° to 140°.

13. A membrane penetrating needle according to claim 12 , wherein the second grind angle (β) is approximately 100°.

14. A membrane penetrating needle according to claim 1 , wherein the needle is provided with a tip angle (β) in the interval 20° to 100°.

15. A membrane penetrating needle according to claim 14 , wherein the tip angle (α) is in the interval 30° to 80°.

16. A membrane penetrating needle according to claim 1 , wherein the needle is provided with a rear angle (β) in the interval 50° to 140°.

17. A membrane penetrating needle according to claim 16 , wherein the rear angle (β) is approximately 100°.

18. A membrane penetrating needle for repeatedly penetrating a membrane, said needle having a pointed end provided with a blunt penetrating tip and with an opening for letting a liquid in and/or out in a main direction which is substantially parallel to the longitudinal extension of the needle, wherein the point of the blunt penetrating tip is rounded and arranged to lie substantially on the longitudinal centre line of the needle when viewed along the longitudinal centre line of the needle, and the blunt penetrating tip is designed with a cross section being substantially triangular with rounded corners causing at least three substantially equally sized forces (F) in different directions which are radial to the longitudinal centre line of the needle and which forces counteract each other so that the needle will tend not to deviate from the initial penetration direction when the needle penetrates a membrane.

19. A membrane penetrating needle according to claim 18 , wherein the cross section of the proximal end of the needle is substantially circular.

20. A membrane penetrating needle according to claim 1 , wherein the rounded point of the blunt penetrating tip is arranged to lie substantially on the longitudinal centre line of the needle.

21. A membrane penetrating needle according to claim 1 , wherein the pointed end has a shape substantially corresponding to a part of an imaginary cone, the tip of which coincides with the rounded point.

22. A membrane penetrating needle according to claim 1 , wherein the pointed end has a shape substantially corresponding to a part of an imaginary cone, the tip of which coincides with the rounded point.

23. A membrane penetrating needle according to claim 1 , wherein the opening is arranged on one and the same half of a cross section of the needle.

24. A membrane penetrating needle according to claim 1 , wherein the pointed end is provided with a basic shape in accordance with a lancet bevel cut.

25. A membrane penetrating needle according to claim 1 , wherein the pointed end is provided with a basic shape in accordance with a back bevel cut.

26. A membrane penetrating needle according to claim 1 , wherein the back bevel cut has a second grind angle (β) in the interval 50° to 140°.

27. A membrane penetrating needle according to claim 1 , wherein the needle is provided with a tip angle (α) in the interval 20° to 100°.

28. A membrane penetrating needle according to claim 1 , wherein the needle is provided with a rear angle (β) in the interval 50° to 140°.