Method for manufacturing a cannula assembly
View Patent ↗The present invention is directed to a novel process for inserting a cannula, such as a hypodermic needle, into a hub member by roughening a first portion of the cannula while leaving a second portion substantially smooth such that the first portion forms an interference fit and the second portion a line-to-line fit with the hub bore. In the absence of an adhesive, the second portion is passed through the hub bore followed by the first portion. The first portion is forced into the hub bore to provide an adhesive-free interference fit that is capable of resisting puncturing forces during normal use.
1. A method for manufacturing a cannula assembly including a hub member and a cannula, comprising the steps of:
forming a roughened exterior surface on a first portion of a cannula such that the first portion of the cannula is roughened and a second portion of the exterior surface of the cannula is substantially smooth; and
inserting the roughened first portion of the cannula into a central bore of a hub, wherein a first radius of the roughened first portion is larger than a radius of the hub bore to form an interference fit therebetween and a second radius of the substantially smooth second portion is the same as or slightly less than the radius of the hub bore to form a line-to-line fit therebetween, and wherein, in the inserting step, the interface between the hub bore and the cannula is free of an adhesive.
2. The method of claim 1 , wherein the forming step includes grit blasting the first portion of the cannula.
3. The method of claim 2 , wherein the roughened exterior surface extends substantially around a circumference of the cannula.
4. The method of claim 1 , wherein the roughened first portion has a length and the cannula a total length and the length of the roughened first portion is from about 25 to about 50% of the total length.
5. The method of claim 1 , wherein the hub is formed from an elastic material such that the central bore expands elastically when the roughened first portion engages the wall of the central bore.
6. The method of claim 5 , wherein the elastic material is selected from the group consisting of a polycarbonate, polystyrene, polypropylene, poly(vinyl chloride), and mixtures thereof.
7. The method of claim 1 , wherein the roughened first portion has a radius and the radius is from about 2.5 to about 30% more than the radius of the substantially smooth second portion.
8. The method of claim 1 , wherein the hub is formed from a material having a flex modulus ranging from about 200,000 psi to about 500,000 psi.
9. The method of claim 1 , wherein the radius of the hub bore is from about 75 to about 99% of the first radius of the roughened first portion of the cannula.
10. The method of claim 1 , wherein the radius of the hub bore is from about 100 to about 125% of the second radius of the substantially smooth second portion of the cannula.
11. The method of claim 1 , wherein the fist radius of the roughened first portion is at least about 0.0001 inches more than the radius of the hub bore.
12. The method of claim 1 , wherein a length of an interface between the hub bore and roughened first portion ranges from about 5 to about 50 mm.
13. The method of claim 1 , wherein a length of the roughened first portion ranges from about 5 to about 50 mm.
14. The method of claim 1 , wherein the bore has a length and the length of the bore is substantially the same as the length of the roughened first portion.
15. The method of claim 1 , wherein the cannula has a pointed end to puncture a surface.
16. The method of claim 1 , wherein a length of the first portion ranges from about 10 to about 25 mm.
17. The method of claim 1 , wherein the second portion is coated at least substantially with a lubricant.
18. The method of claim 1 , wherein the cannula is a hypodermic needle.
19. A method for manufacturing a cannula assembly including a hub member and a cannula, comprising the steps of:
(a) grit blasting a first portion of a cannula such that the grit blasted first portion of the cannula's exterior surface is roughened relative to a second portion of the exterior surface that is substantially smooth;
(b) inserting the substantially smooth second portion of the cannula into a bore of a hub member;
(c) after, the inserting step (b), forcing the substantially smooth second portion to pass through the bore;
(d) inserting the grit blasted first portion of the cannula into the bore; and
(e) forcing at least most of the grit blasted first portion of the cannula into a frictional fit with the hub bore, wherein a first radius of the roughened first portion is larger than a radius of the bore to form an interference fit therebetween and a second radius of the substantially smooth second portion is the same as or slightly less than the radius of the bore to form a line-to-line fit therebetween, and wherein, in the inserting step, the interface between the bore and the cannula is free of an adhesive.
20. The method of claim 19 , wherein the roughened exterior surface of the first portion extends substantially around a circumference of the cannula.
21. The method of claim 19 , wherein the roughened first portion has a length and the cannula a total length and the length of the roughened first portion is from about 25 to about 50% of the total length.
22. The method of claim 19 , wherein the hub member is formed from an elastic material such that the bore expands elastically when the roughened first portion engages the wall of the bore.
23. The method of claim 22 , wherein the elastic material is selected from the group consisting of a polycarbonate, polystyrene, polypropylene, poly(vinyl chloride), and mixtures thereof.
24. The method of claim 19 , wherein the roughened first portion has a radius and the radius is from about 2.5 to about 30% more thn the radius of the substantially smooth second portion.
25. The method of claim 19 , wherein the hub member is formed from a material having a flex modulus ranging from about 200,000 psi to about 500,000 psi.
26. The method of claim 19 , wherein the radius of the bore is from about 75 to about 99% of the radius of the roughened first portion of the cannula.
27. The method of claim 19 , wherein the radius of the bore is from about 100 to about 125% of the radius of the substantially smooth second portion of the cannula.
28. The method of claim 19 , wherein the radius of the roughened first portion is at least about 0.0001 inches more than the radius of the bore.
29. The method of claim 19 , wherein a length of an interface between the bore and roughened first portion ranges from about 5 to about 50 mm.
30. The method of claim 19 , wherein a length of the roughened first portion ranges from about 5 to about 50 mm.
31. The method of claim 19 , wherein the bore has a length and the length of the bore is substantially the same as the length of the roughened first portion.
32. The method of claim 19 , wherein a length of the first portion ranges from about 10 to about 25 mm.
33. The method of claim 19 , wherein the second portion is coated at least substantially with a lubricant.
34. The method of claim 19 , wherein the cannula is a hypodermic needle.