WO2001066179A1

WO2001066179A1 - Hypodermic syringe with retractable needle

Info

Publication number: WO2001066179A1
Application number: PCT/US2001/006977
Authority: WO
Inventors: Thor R. Halseth; John Barker; Michael J. Botich
Original assignee: Mdc Investment Holdings, Inc.
Priority date: 2000-03-06
Filing date: 2001-03-06
Publication date: 2001-09-13
Also published as: US7527607B2; US20030208164A1; AU2001243420A1

Abstract

A safety needle-bearing medical advice (10) is provided. Specifically, a safety device for injecting medicinal fluid into a patient is provided. The device comprises a hollow housing (20), a needle assembly (40) and a plunger (30). The needle assembly (40) releasably retains a needle (45) in an extended position in which the sharpened tip of the needle is exposed for use. At the end of an injection stroke, the plunger (30) engages the needle assembly (40), such that the needle (45) is released and retracted into a cavity (38) within the plunger. The device (10) includes structure for reducing the dead-space volume, which represents the amount a fluid remaining in the device at the end of an injection stroke. In addition, preferably the device (10) includes structure for minimizing the volume of potential air bubbles trapped in the medicinal fluid prior to an injection.

Description

HYPODERMIC SYRINGE WITH RETRACTABLE NEEDLE

Field of the Invention

The present invention relates to syringes for administering injections

of medicinal fluids to a patient or withdrawal of fluid, such as blood from

a patient. More specifically, the invention relates to such devices having a

retractable needle feature for rendering the device non-reusable and safely

disposable.

Background of the Invention

Various types of medical devices employ a needle for piercing the

skin of a patient for diagnostic or therapeutic purposes. One such device

is a hypodermic syringe. Handling of such needle-bearing medical devices

after the needle is withdrawn from the patient can result in transmission

of various pathogens, most notably human immune virus (HIV), to

uninfected medical personnel, due to an inadvertent needle stick.

Accordingly, it is desirable to provide a device for injecting medication or

withdrawing fluid, wherein the needle is retracted into the housing of the

device after use.

The following detailed description of the preferred embodiments will

be better understood when read in conjunction with the figures, in which:

Fig. 1 is an exploded perspective view of a safety hypodermic syringe having a retractable needle, manifesting aspects of the present invention;

Fig. 2 is an exploded perspective view of a needle subassembly of the

syringe illustrated in Fig. 1 ;

Fig. 3 is an exploded perspective view of a plunger subassembly of the

syringe illustrated in Fig. 1 ;

Fig. 4 is a cross-sectional view of the syringe illustrated in Fig. 1 ;

Fig. 5 is a cross-sectional view of the syringe illustrated in Fig. 4, showing

the needle in a retracted position;

Fig. 6 is an enlarged fragmentary cross-sectional view of the forward end

of the syringe illustrated in Fig. 1 ;

Fig. 7 is an enlarged fragmentary cross-sectional view of the forward end

of the syringe illustrated in Fig. 1 , orthogonal to Fig. 6;

Fig. 8 is an enlarged fragmentary cross-sectional view of the forward end

of the barrel of the syringe illustrated in Fig. 1 ; and

Figure 9 is an enlarged fragmentary cross-sectional view of the forward end of the barrel of the syringe illustrated in Fig. 1 , orthogonal to Fig. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures in general, and more specifically to Fig.

1 , a retractable needle safety hypodermic syringe is designated generally

1 0. The syringe 1 0 includes a barrel 20, a plunger 30 reciprocally

displaceable within the barrel, and a needle assembly 40 attachable to the

forward end of the barrel. The needle assembly releasably retains a

needle 45, such that after use, the needle is retracted into the barrel 20,

so that the needle is shielded after use to prevent inadvertent contact

with the contaminated needle after use.

The barrel is a generally hollow cylinder having a tip 22 configured

to cooperate with the needle assembly 40. The rearward end of the

barrel is generally open for receiving the plunger 30. The plunger 30 is

reciprocally displaceable within the barrel for drawing fluid into the barrel

or expelling fluid from the barrel.

The plunger 30 comprises a substantially rigid elongated plunger

rod 32 and a piston 35 attach to the forward end of the plunger rod 32.

The piston 35 forms a fluid tight seal with the interior surface of the

barrel 20. As discussed further below, the piston 35 is axially compressible at the end of the injection stroke to reduce the dead space

at the forward end of the barrel. Dead space refers to the volume in the

barrel in which a fluid can reside at the end of an injection stroke.

Effectively, the dead space volume of a syringe is the amount of

medication that is wasted because the fluid in the dead space cannot be

injected.

The forward end or head 33 of the plunger rod 32 is configured to

matingly engage the needle assembly 40. In the present instance, the

plunger head 33 is substantially frustoconical. The plunger rod 32 is

hollow, having a cavity 38 for receiving the needle 45 after retraction.

The plunger head 33 has an opening or orifice through which the needle

passes into the cavity 38 during retraction. This orifice is sealed by a

displaceable plug 36. The plunger rod may be a substantially hollow

cylinder. However in the present instance, the plunger rod is 80 generally

u-shaped channel having an opened top edge as shown in Figs. 4 and 5.

The plunger rod further comprises a circumferential flange 37 adjacent

the rearward end wall of the cavity 38. The flange 37 is a locking

element that mates with an annular rib 28 that protrudes inwardly from

the inner surface of the barrel 20. The locking flange 37 and the locking

rib 28 lock the plunger 30 against rearward displacement at the end of an

injection stroke. Specifically, as the plunger 30 is displaced forwardly, the

locking flange 37 rides over the rearward face of the locking rib 28, which is tapered. The forward face of the locking rib 28 forms a substantially

square shoulder that cooperates with the flange 37 to impede rearward

displacement of the plunger 30.

Referring now to Fig. 2, the details of the needle assembly 40 are

most clearly seen. The needle assembly 40 includes the needle 45, a

spring 75 biasing the needle rearwardly, a needle retainer 50 releasably

retaining the needle against the bias of the spring, a needle fitting 60

attached to the rearward end of the needle to provide an engagement

surface for the needle retainer, and a cap 70 enclosing the forward end of

the needle assembly.

The needle retainer 50 comprises a pair of radially deformable

axially elongated fingers 54 extending rearwardly from a substantially

cylindrical body 52. The rearward portion of the cylindrical body 52 is

configured to form an interference fit with the interior of the tip 22 of the

barrel 20. In this way, a fluid tight seal is formed between the needle

retainer 50 and the tip 22 so that fluid cannot leak out of the barrel

between the tip 22 and the needle retainer 50. The needle retainer 50

has a bore for receiving the needle fitting 60. The fingers 54 have

inwardly projecting latches engaging the rearward end of the needle fitting

60 to retain the needle against the rearward bias of the spring 75. The needle fitting is a hollow substantially cylindrical element. The

rearward end of the needle fitting 60 flares outwardly forming a generally

frustoconical head. The frustoconical head mates with the inner surface

of the fingers 54. Adjacent the frustoconical head 62 is an annular

sealing rib 67 that protrudes from the surface of the needle fitting. The

sealing rib 67 forms an interference fit with the inner bore of the needle

retainer 50 to form a fluid-tight seal between the needle fitting 60 and the

inner bore of the needle retainer. However, the interference fit between

the sealing rib 67 and the needle retainer 50 is not sufficient to retain the

needle against the rearward bias of the spring 75. The inner bore of the

needle fitting forms a reservoir for receiving the rearward end of the

needle and epoxy for bonding the needle to the needle fitting. The

lowermost portion of the reservoir forms a plenum 63 in fluid

communication with the needle 45. The reservoir is constricted forward

of the plenum 63 to a diameter closely corresponding to the outer

diameter of the needle. In this way, the constriction operates to center

the needle within the reservoir.

A vent passage 64 in fluid communication with the plenum 63

extends through the width of the needle fitting head 62. The vent

passage 64 provides fluid communication between the interior of the

barrel 20 and the plenum 63. If the vent passage is aligned with the

needle retainer fingers 54 so that the fingers overlap the vent passages, fluid flow through the vent passages will be either blocked or reduced.

Accordingly, the fingers 54 should be located so that they do not overlap

with the vent passages 64. Alternatively, and preferably, a

circumferential vent groove 65 may be formed on the exterior surface of

the needle. fitting rearward of the sealing rib 67. The vent groove 65

intersects the vent passage 64 to form a fluid pathway around the fingers

54 to eliminate any problems associated with blockage of the vent

passage 64 by the fingers. Configured in this manner, the fluid seal

between the needle retainer and the barrel is immediately adjacent the

fluid seal between the needle fitting and the needle retainer, and the fluid

passage through the needle fitting and to the needle 45 is immediately

rearward of the fluid seal between the needle fitting and the needle

retainer. Since the fluid passage is immediately adjacent the rearward-

most fluid seal, the space within the device in which air bubbles could

potentially become trapped is minimized .

The cap 70 is a hollow cylinder having a generally closed forward

end with a reduced diameter opening. The forward end of the needle

fitting 60 has a reduced diameter portion configured to project through

the reduced diameter opening of the cap. A plurality of axially spaced

circumferential ridges are formed on the interior surface of the cap. The

cap ridges cooperate with a plurality of corresponding axially spaced

circumferential locking ridges 56 on the exterior of the needle retainer 50. In this way, the cap and the needle retainer enclose the needle assembly

40 so that the needle assembly is a separable assembly that can be

attached to the barrel 20. As shown in Fig. 6, the spring 75 is disposed

within the needle retainer 50 circumscribing the needle fitting 60 bearing

against the cap 70 and the head 62 of the needle fitting.

Referring again to Fig. 1 , the tip 22 of the barrel 20 comprises a

pair of locking windows 27 that cooperate with a pair of locking tabs 55

on the needle assembly 40 to attach the needle assembly to the barrel.

The tip 22 includes a pair of axial alignment grooves 26 extending

between the locking windows 27 and the forward end of the tip. The

alignment grooves 26 are configured to receive the locking tabs 55 to

provide proper alignment between the needle assembly 40 and the barrel

20 so that the locking tabs 55 are aligned with the locking windows 27.

The tip further comprises a pair of opposing clearance grooves 25

aligned with the needle retainer fingers 54. The clearance grooves 25

provide space for the outward radial displacement of the fingers 54. The

tip 22 further includes a plurality of protrusions 24 projecting inwardly

from the inner surface of the tip to fill the space adjacent the area in

which the needle retainer fingers 54 are received. The protrusions 24

reduce the area between the fingers 54 and the interior of the tip, other

than the clearance grooves 25 for the fingers. In this way the protrusions 24 substantially reduce the dead space between the needle retainer and

the interior of the tip.

Configured in this manner, the device operates as follows. The

needle assembly 40 is inserted into the tip 22 of the barrel so that the

locking tabs 55 of the needle retainer 50 are aligned with the alignment

grooves 26 of the tip. The needle assembly 40 is inserted into the tip

until the locking tabs 55 engage the locking windows 27 to substantially

permanently attach the needle assembly to the barrel 20.

The fluid is drawn into the barrel by inserting the sharpened tip of

the needle 45 into a fluid container and drawing the plunger 30

rearwardly. The needle 45 is then inserted into a patient and the fluid is

injected into the patient by displacing the plunger 30 forwardly. At the

end of the injection stroke, the head 33 of the plunger rod 32 engages the

fingers 54 of the needle retainer 50 and the piston 35 engages the

forward end of the barrel 20. Continued forward displacement of the

plunger axially compresses the piston 35 and drives the frustoconical head

of the plunger rod against the inwardly tapered surfaces of the fingers 54,

thereby wedging the fingers apart. In other words, the plunger radially

displaces the fingers outwardly. At the same time, the plug 36 that seals

the opening at the forward end of the plunger engages the head 62 of the

needle fitting 60, displacing the plug rearwardly into the cavity of the plunger so the plunger opening is not obstructed. Once the fingers 54 are

displaced radially outwardly out of engagement with the needle fitting, the

needle is released and the spring 75 propels the needle and attached

needle fitting rearwardly into the cavity 38 in the plunger so that the

sharpened tip of the needle is shielded against inadvertent contact.

Claims

1. A safety medical device, comprising: a hollow housing; a needle having a sharpened tip operable between an extended position in which the needle is exposed for use and a retracted position in which the needle is shielded against inadvertent contact; a spring biasing the needle toward the retracted position; a needle retainer releasably maintaining the needle in the extended position;

an actuator slidable within the housing wherein after use of the device, the actuator automatically engages the needle retainer to actuate retraction to displace the needle into the retracted position.

2. The safety medical device of claim 1 wherein the actuator is a plunger operable to expel fluid from the housing.

3. The safety medical device of claim 1 comprising a first seal providing a fluid-tight seal between the needle retainer and the housing.

4. The safety medical device of claim 3 comprising a second seal providing a fluid-tight seal between the needle retainer and the needle to prevent fluid from leaking through the needle retainer between the needle and the needle retainer.

5. The safety medical device of claim 4 comprising a block attached to the needle, wherein the block includes an opening so that the needle is in fluid communication with the interior of the housing.

6. The safety medical device of claim 5 wherein the first seal is adjacent the second seal.

7. The safety medical device of claim 5 or 6 wherein the opening in the block is adjacent the second seal.

8. The safety medical device of claim 2, wherein the housing comprises a fluid cavity for receiving medicinal fluid, and the plunger is operable to expel fluid from the fluid cavity through the needle.

9. The safety medical device of claim 8 wherein the plunger comprises an axially compressible piston forming a fluid-tight seal with the interior of the housing.

10. The safety medical device of claim 9 wherein the fluid cavity comprises

a forward end wall, and the piston engages the forward end wall prior to actuation of retraction, wherein continued forward displacement of the plunger after the piston engages the forward end wall operates to axially compress the piston such that the plunger engages the needle retainer to effectuate retraction.

11. A safety medical device, comprising: a hollow housing having a fluid cavity; a needle assembly, comprising:

a needle having a sharpened tip; a needle hub attached the needle, comprising an interior cavity forming a plenum, and a fluid passage in fluid communication with the housing fluid cavity, wherein the needle and fluid passage are in fluid communication with the plenum; a needle retainer releasably engaging the needle hub to retain the needle in a projecting position in which the sharpened tip projects forwardly from the housing so that it is

exposed for use, wherein the needle comprises a bore and the needle hub is disposed within the bore, forming a fluid-tight seal between the needle hub and the bore; and a biasing element biasing the needle rearwardly into a retracted position in which the sharpened tip is shielded to prevent

inadvertent contact with the sharpened tip; and a plunger axially displaceable within the housing to expel fluid from the housing, wherein the plunger comprises a hollow cavity for receiving the needle when the needle is displaced into the retracted position.

12. The safety medical device of claim 11 wherein the needle retainer comprises a pair of radially deformable latches engaging the needle hub, and the plunger comprises an actuation surface operable to displace the latches radially thereby disengaging the needle hub from the needle retainer.

13. The safety medical device of claim 11 wherein the housing comprises a protrusion projecting radially inwardly adjacent the needle retainer to reduce the interior volume of the housing between the needle retainer and the housing.

14. The safety medical device of claim 13 wherein the needle retainer comprises a radially displaceable arm engaging the needle hub, and the housing comprises a channel aligned with the arm, adjacent the protrusion, for receiving the arm when the arm is displaced radially.

15. The safety medical device of claim 11 wherein the needle hub comprises a circumferential groove intersecting the fluid passage.

16. The safety medical device of claim 11 comprising a seal between the needle retainer and the housing, forming a fluid-tight seal.

17. The safety medical device of claim 16 wherein the fluid passage in the needle hub comprises an inlet opening adjacent to, and rearward of, the seal.

18. A safety medical device comprising: a hollow housing for receiving a quantity of medicinal fluid, wherein the fluid may include air bubbles; a needle having a sharpened tip operable in an extended position in which the sharpened tip is exposed for use, and a retracted position in which the sharpened tip is shielded; a biasing element biasing the needle toward the retracted position; means for releasably retaining the needle against the biasing element; a plunger axially displaceable in the housing to expel fluid from the housing during an injection; and means for minimizing residual air bubbles in the medicinal fluid prior to the injection; wherein upon forward advancement of the needle after injection, the plunger engages the means for releasably retaining the needle to release the needle, whereby the biasing element displaces the needle into the retracted position.