Valved blood sampling needle assembly

Claim 1

A needle assembly for facilitating the collection of a blood sample from a patient into an evacuated collection container while preventing flow of fluid from the collection container into the patient during and after collection of the blood sample comprising: a housing having a forward end with an opening therein and a rear end with an opening therein with both openings extending into a central chamber in the housing; a first double ended substantially rigid cannula having a passage therethrough mounted in fixed position in the opening in the forward end of the housing with the forward end of the cannula being pointed for venipuncture and the rear end of the cannula in the chamber of the housing; a second double ended substantially rigid cannula having a passage therethrough mounted in fixed position in the opening in the rear end of the housing with the passage opening in the forward end of the second cannula in fluid communication with the chamber in the housing through the opening in the rear end of the housing and the rear end of the second cannula being pointed for insertion into an evacuated collection container thereby providing a continuous passage from the forward end of the first cannula to the rear end of the second cannula; a resilient cylindrically shaped cap of elastomeric self-sealing material having an open end and a closed end; the opening in the open end extending a substantial distance throughout the length of the cap and being of normally lesser diameter in at least the portion adjacent the open end than the outer diameter of the rear end of the first cannula; the cap being mounted on the rear end of the first cannula in the chamber with the portion of the cap on the cannula in expanded condition so as to fit thereon in tight sealing engagement therewith; and at least one slit in the cap aligned with the opening therein and spaced from the portion of the cap mounted on the first cannula with the sliT being normally closed; so as to close the passageway through the assembly and being responsive to a reduction in fluid pressure at the rearward end of the second cannula to resiliently deform independent of any force other than the reduction in fluid pressure and independent of orientation of the assembly so as to automatically open the passageway through the assembly, and thereafter be responsive to a predetermined increase in fluid pressure at the rearward end of the second cannula to automatically return to the closed position independent of any other force than the increase in fluid pressure and independent of orientation of the assembly.