GB1574187A

GB1574187A - Low-dose hypodermic syringe

Info

Publication number: GB1574187A
Application number: GB743877A
Authority: GB
Original assignee: Becton Dickinson and Co
Current assignee: Becton Dickinson and Co
Priority date: 1976-07-06
Filing date: 1977-02-22
Publication date: 1980-09-03
Also published as: AU2263577A; BE852155A; DE2703213C3; JPS535891A; DE2703213A1; FR2357261A1; FR2357261B1; BR7701823A; DE2703213B2; AU501347B2; JPS573375B2

Description

(54) LOW-DOSE HYPODERMIC SYRINGE (71) We, BECrON, DICKINSON & COMPANY, a corporation organized and existing under the laws of the State of New Jersey, United States of America, located at Stanley and Cornelia Streets, East Rutherford, New Jersey, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a low-dose hypodermic syringe.

In low-dose hypodermic syringes, the component parts are normally small while the forces generated during injection are high. Problems have been experienced in initially creating a liquid-tight seal between a needle assembly and a tubular barrel of the syringe and maintaining the seal during removal of a needle sheath and injection of the contained liquid. With syringes having a capacity of 21 cc or less, accuracy in the amount of liquid injected becomes critical in assuring proper medication and therapy.

A standard luer connection is frequently used to connect the needle assembly and the tubular barrel of the syringe; however this connection is not entirely satisfactory for low-dose syringes and has a total internal volume which is significantly more than that of the main barrel chamber so that the syringe must be filled with excess medicament to compensate for this volume when measuring dosage. After administration a residual volume of medicament remains in the syringe tip and needle hub lumen. Thus, when two or more medicaments are measured in the same syringe, the excess or residual volume will create an error of their relative ratio-in the resultant mixture.

It is- an object of the present invention to obviate or mitigate the above-described problems.

According to the present invention there is provided a low-dose hypodermic syringe comprising a tubular barrel having a boss extending from one end thereof, a piston slidable within the barrel and connected to a plunger rod extending from the opposite end of the barrel, the boss defining an end wall of the barrel against which the piston abuts in dispensing liquid from the syringe and having a female frustoconical opening therein, a hub having a radial flange and a male frustoconical extension whose shape matches, that of the female frustoconical opening in the boss, the male extension being inserted in the female opening so as to provide a leak-proof seal therebetween with an end of the male extension remote from the radial flange being substantially flush with the internal surface of said end wall of the barrel, the hub also having a collar which is integral with the radial flange and which surrounds the male extension so as to be manually graspable for attaching the hub to and removing the hub from the boss, the collar having a radially inwardly extending projection which frictionally engages an outer surface of the boss to provide a mechanical lock of the hub on the boss, and a hollow needle having an end thereof secured to the hub, a lumen which extends through the needle terminating substantially co-incidently with said remote end of the male extension.

In this way, the needle assembly (i.e. the needle and the hub) can be securely attached to the tubular barrel so that it does not become detached therefrom during removal of a needle sheath or during the actual injection process. Moreover, the fact that said remote end of the hub male extension is substantially flush with the internal surface of the end wall of the barrel, and the fact that the lumen which extends through the needle terminates substantially co-incidentally with said remote end of the hub male extension enables the residual volume of liquid over the measured volume of the syringe to be kept to a minimum. The syringe also operates in an efficient manner and is simple to manufacture and use.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded side view of a low-dose hypodermic syringe according to the present invention; Figure 2 is a side view, partly in section, of a needle assembly of the syringe, with a needle thereof removed for clarity; Figure 3 is a sectional side view of the needle assembly shown in Figure 2; Figure 4 is a front end view of the needle assembly; Figure 5 is a rear end view of the needle assembly; and Figure 6 is a side view, partly in section of one end of the hypodermic syringe shown in Figure 1.

Referring to the drawings, the hypodermic syringe shown therein is of the low-dose type and comprises a plastics tubular barrel 10 having a boss 14 of reduced diameter extending integrally from one end thereof.

A piston is slidabIe within an internal chamber 42 of the barrel 10 to dispense liquid contained therein, the boss 14 defining an end wall of the barrel 10 against which the piston abuts in dispensing the liquid from the syringe. The piston is connected to a plunger rod 12 which extends from a widened end 18 of the barrel 10 remote from the boss 14, the widened end 18 having an outward taper 22 which serves as a lead-in for the piston and the plunger rod 12 during assembly of the syringe.

A - -needle assembly 24 is attached to the barrel 10 and comprises a plastics hub 26 to which one end of a cannula or needle 30 is secured by means of suitable epoxy cement 32 dispensed in an annular recess 34. The hub 26 includes a radial flange 46 and an integral male frustoconical extension 28, the needle 30 being mounted on the hub 26 such that a bore 36 which extends therethrough terminates substantially co-incidently with an end of the male extension 28 remote from the radial flange 46. A radially inwardly extending flange 38 is provided at said remote end of the male extension 28 and serves as a stop when the needle is inserted into the hub during assembly. The flange 38 has a passageway or bore therein which generally conforms in size to the bore 36 of the needle 30. This passageway and the bore of the needle together form a lumen of the needle assembly.

The needle assembly 24 is attached to the barrel 10 by inserting the male extension 28 on the hub 26 into a female frustoconical opening 16 in the boss 14. When the extension 28 is thus inserted,. the said remote erid thereof is substantially flush with the 'mtnal surface 40 of the end wall of the barrel 10, so that there is no significant residual volume beyond that of the barrel cOhbèr i2 and the total volume within the Syringe is substantially equal to the measured syringe volume. The shape of the frusto coiricsd extension 28 substantially matches that of the opening 16 so that a liquid-tight seal - is formed therebetween, thereby preventing leakage of the dispensed liquid during injection.

The hub 26 also includes a collar 48 which is integral with the radial flange 46 and which extends rearwardly therefrom so as to surround the extension 28. The collar 48 not only provides means for gripping the needle assembly for attaching it to and removing it from the barrel 10, but also provides a mechanical lock of the needle assembly on the barrel 10. To this end, the collar 48 has an internal surface 52 which is an interference fit with an external surface 50 of the boss 14, and also has a radially inwardly extending bead or flange 54 which frictionally and tightly engages the surface 50 of the boss 14. Inasmuch as the barrel 10 and the hub 26 are moulded from a suitable resin, such as polypropylene, the bead 54 will in time form a depression in the surface 50 (as shown in Figure 6) to complete the mechanical interlock. In this way, the liquid-tight seal between the engaging surfaces of the frustoconical extension 28 and the opening 16 is assured and maintained during removal of a needle sheath 56 (see Figure 1) and while the contained liquid is injected. Obviously, forms of radially inwardly extending projections other than the bead 54 can be utilized to form the mechanical interlock between the hub 26 and the boss 14.

WHAT WE CLAIM IS: 1. A low-dose hypodermic syringe comprising a tubular barrel having a boss extending from one end thereof, a piston slidable within the barrel and connected tp a plunger rod extending from the opposite end of the barrel, the boss defining an end wall of the barrel against which the piston abuts in dispensing liquid from the syringe and having a female frustoconical opening therein, a hub having a radial flange and a male frustoconical extension whose shane matches that of the female frustoconical opening in the boss, the male extension being inserted in the female opening so as to provide a leak-proof seal therebetween with an end of the male extension remote from the radial flange being substantially flush with the internal surface of said end wall of the barrel, the hub also having a collar which is integral with the radial flange and which surrounds the male extension so as to be manually graspable for attaching the hub to and removing the hub from the boss, the collar having a radially inwardlv extending projection which frictionally engages an outer surface of the boss to provide a mechanical lock of the hub on the boss, and a hollow needle having an end thereof secured to the hub, a lumen which

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. low-dose hypodermic syringe according to the present invention; Figure 2 is a side view, partly in section, of a needle assembly of the syringe, with a needle thereof removed for clarity; Figure 3 is a sectional side view of the needle assembly shown in Figure 2; Figure 4 is a front end view of the needle assembly; Figure 5 is a rear end view of the needle assembly; and Figure 6 is a side view, partly in section of one end of the hypodermic syringe shown in Figure 1. Referring to the drawings, the hypodermic syringe shown therein is of the low-dose type and comprises a plastics tubular barrel 10 having a boss 14 of reduced diameter extending integrally from one end thereof. A piston is slidabIe within an internal chamber 42 of the barrel 10 to dispense liquid contained therein, the boss 14 defining an end wall of the barrel 10 against which the piston abuts in dispensing the liquid from the syringe. The piston is connected to a plunger rod 12 which extends from a widened end 18 of the barrel 10 remote from the boss 14, the widened end 18 having an outward taper 22 which serves as a lead-in for the piston and the plunger rod 12 during assembly of the syringe. A - -needle assembly 24 is attached to the barrel 10 and comprises a plastics hub 26 to which one end of a cannula or needle 30 is secured by means of suitable epoxy cement 32 dispensed in an annular recess 34. The hub 26 includes a radial flange 46 and an integral male frustoconical extension 28, the needle 30 being mounted on the hub 26 such that a bore 36 which extends therethrough terminates substantially co-incidently with an end of the male extension 28 remote from the radial flange 46. A radially inwardly extending flange 38 is provided at said remote end of the male extension 28 and serves as a stop when the needle is inserted into the hub during assembly. The flange 38 has a passageway or bore therein which generally conforms in size to the bore 36 of the needle 30. This passageway and the bore of the needle together form a lumen of the needle assembly. The needle assembly 24 is attached to the barrel 10 by inserting the male extension 28 on the hub 26 into a female frustoconical opening 16 in the boss 14. When the extension 28 is thus inserted,. the said remote erid thereof is substantially flush with the 'mtnal surface 40 of the end wall of the barrel 10, so that there is no significant residual volume beyond that of the barrel cOhbèr i2 and the total volume within the Syringe is substantially equal to the measured syringe volume. The shape of the frusto coiricsd extension 28 substantially matches that of the opening 16 so that a liquid-tight seal - is formed therebetween, thereby preventing leakage of the dispensed liquid during injection. The hub 26 also includes a collar 48 which is integral with the radial flange 46 and which extends rearwardly therefrom so as to surround the extension 28. The collar 48 not only provides means for gripping the needle assembly for attaching it to and removing it from the barrel 10, but also provides a mechanical lock of the needle assembly on the barrel 10. To this end, the collar 48 has an internal surface 52 which is an interference fit with an external surface 50 of the boss 14, and also has a radially inwardly extending bead or flange 54 which frictionally and tightly engages the surface 50 of the boss 14. Inasmuch as the barrel 10 and the hub 26 are moulded from a suitable resin, such as polypropylene, the bead 54 will in time form a depression in the surface 50 (as shown in Figure 6) to complete the mechanical interlock. In this way, the liquid-tight seal between the engaging surfaces of the frustoconical extension 28 and the opening 16 is assured and maintained during removal of a needle sheath 56 (see Figure 1) and while the contained liquid is injected. Obviously, forms of radially inwardly extending projections other than the bead 54 can be utilized to form the mechanical interlock between the hub 26 and the boss 14. WHAT WE CLAIM IS:

1. A low-dose hypodermic syringe comprising a tubular barrel having a boss extending from one end thereof, a piston slidable within the barrel and connected tp a plunger rod extending from the opposite end of the barrel, the boss defining an end wall of the barrel against which the piston abuts in dispensing liquid from the syringe and having a female frustoconical opening therein, a hub having a radial flange and a male frustoconical extension whose shane matches that of the female frustoconical opening in the boss, the male extension being inserted in the female opening so as to provide a leak-proof seal therebetween with an end of the male extension remote from the radial flange being substantially flush with the internal surface of said end wall of the barrel, the hub also having a collar which is integral with the radial flange and which surrounds the male extension so as to be manually graspable for attaching the hub to and removing the hub from the boss, the collar having a radially inwardlv extending projection which frictionally engages an outer surface of the boss to provide a mechanical lock of the hub on the boss, and a hollow needle having an end thereof secured to the hub, a lumen which

extends through the needle terminating substantially co-incidently with said remote end of the male extension.

2. A hypodermic syringe as claimed in Claim 1, wherein the projection on the collar is in the form of a radially inwardly extending bead.

3. A hypodermic syringe as claimed in Claim 1 or 2, wherein the tubular barrel and the hub are made of plastics material.

4. A hypodermic syringe as claimed in Claim 1, 2 or 3, wherein the needle is cemented to the hub.

5. A low-dose hypodermic syringe substantially as hereinbefore described with reference to the accompanying drawings.