Technical Field Of The Invention

In general, the present invention relates to syringes that are used to make injections through a needle or cannula . More particularly, the present invention relates to multiple dose syringes that are designed to minimize the amount of injection material retained within the syringe after the syringe is used for the last dose.

Background Art

Millions of injections are performed in the United States of America each year. The injections are typically performed using a hypodermic needle and a syringe. The length of the hypodermic needle and the gauge of the needle depend upon the

application and whether the injection

is intramuscular, subcutaneous, intravenous, or intradermal . The compounds being injected also varywidely. Some injection materials, such as saline, are very inexpensive. However, many pharmaceutical compounds, such as certain gene therapy compounds, can cost tens of thousands of dollars per injection. As such, a fraction of a milliliter of the

pharmaceutical can be worth hundreds of dollars. When a traditional hypodermic needle and syringe are used to perform an injection, there is inevitably some volume of injection material that remains within the needle and syringe after the injection is complete . The pharmaceutical material remaining is thrown away with the needle and syringe after the injection. This wasted pharmaceutical material adds up to billions of dollars in wasted pharmaceuticals , when all injections are considered.

In the prior art, thought is rarely given to the volume of residual material that inherently remains within a hypodermic syringe and needle. Some needle and syringe assemblies have been designed where a syringe plunger and a needle head make flush contact. Such prior art designs are exemplified by

U.S. Patent No. 6,616,636 to Lee and U.S. Patent No.

5,902,270 to Jentzen. However, in a real healthcare environment, such as a hospital, different syringes are used with many different needle heads, depending upon the specific medical application. Some needle head and syringe combinations are efficient in the discharge of pharmaceutical compounds and some are not .

The problem becomes more complicated when a needle head and syringe are part of a safety syringe assembly. Safety syringe assemblies are designed to both perform an injection and to provide some mechanism for minimizing the likelihood of a needle stick injury. Needle stick injuries are commonplace among healthcare workers. Needle stick injuries are defined by the United States National Institute of Occupational Safety and Health as injuries caused by needles such as hypodermic needles, blood collection needles, intravenous (IV) stylets, and needles used to connect parts of IV delivery systems. Needle stick injuries can transfer blood-borne pathogens such as Hepatitis B virus, Hepatitis C virus, Human Immunodeficiency Virus (HIV) and Covid-19. For healthcare workers, needle stick injuries are responsible for a significant proportion of these diseases in the healthcare workforce.

It has been estimated by the Centers for

Disease Control, that in the United States of

America, more than three million healthcare workers are exposed to blood and bodily fluids via needle mishaps each year. Most healthcare workers are trained in procedures for using and disposing of used needles. For example, needles should not be recapped, in order to prevent the potential for needle stick injuries. However, many studies have revealed that recapping is still prevalent among healthcare workers . In an attempt to reduce the number of needle stick injuries, various safety needles have been developed that act to automatically cover a needle the instant the needle is retracted from the skin. This is typically accomplished by advancing a tubular sheath along the shaft of the needle until the sheath covers the tip of the needle. Such prior art is exemplified by U.S. Patent No. 6,626,863,

U.S. Patent Application Publication No.

2007/0016140, U.S. Patent Application Publication No. 2007/0016145, and U.S. Patent Application

Publication No. 2008/009808. However, integrating a safety mechanism within a needle head typically takes additional room within the needle head. More room in the needle head means that there is more dead space in the needle head where residual pharmaceutical compounds can collect. As a

consequence, there are often opposing concerns that must be balanced in a design. The safety features of a design are balanced with the wasted pharmaceutical retained because of the safety features .

A need therefore exists for an improved hypodermic needle and syringe assembly where the needle is automatically shielded after an injection and wherein the assembly does not retain any significant volume of the material being injected. This need is met by the present invention as described and claimed below.

DISCLOSURE OF THE INVENTION

The present invention is a needle and syringe system, wherein a needle head is attached to a syringe assembly. The syringe assembly contains a barrel and a plunger. The plunger has a bore opening formed in one end that is accessible from within the barrel .

A tubular spacer is disposed within the barrel. The tubular spacer defines a central opening that extends through the tubular spacer .

The needle head selectively attaches to the syringe assembly. The needle head has a needle that extends from a needle base. The needle base extends into the central opening of the tubular spacer.

A plug is provided inside the barrel that blocks access to the needle by blocking the central opening of the tubular spacer. The plug is displaced out of the central opening of the tubular spacer and into the opening in the plunger as the plunger contacts and displaces the tubular spacer in the barrel. As the plug is displaced from the tubular spacer, the plug transfers into the bore opening within the plunger. This enables the plunger to press flush against the tubular spacer.

As the tubular spacer is displaced by the plunger, the tubular spacer moves a safety sheath that advances and covers the needle, therein rendering the needle safe.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, considered in conjunction with the accompanying drawings, in which: FIG. 1 shows the head of a needle and syringe system in a condition ready for use with its needle exposed;

FIG. 2 is a cross-sectional view of the exemplary embodiment of Fig. 1;

FIG. 3 is an exploded cross-sectional view of the exemplary embodiment of Fig. 1; FIG. 4 is a cross-sectional view of a head subassembly prior to attachment with a syringe subassembly;

FIG. 5 is a cross-sectional view of the exemplary embodiment of Fig. 1 showing material being drawn into the needle and syringe system;

FIG. 6 shows a cross-section of the exemplary embodiment of Fig. 1 showing material being

displaced from the needle and syringe system; and

FIG. 7 shows a cross-section of the exemplary embodiment of Fig. 1 showing all material displaced from the needle and syringe system.

DETAILED DESCRIPTION OF BEST MODE FOR CARRYING OUT THE INVENTION

The present invention needle and syringe system can be configured in many ways and can be adapted for use in many applications. However, only one exemplary embodiment is selected for the purposes of description and illustration. The illustrated embodiment, however, is merely exemplary and should not be considered a limitation when interpreting the scope of the appended claims . Referring to Fig. 1, Fig. 2, and Fig. 3, the present invention needle and syringe system 10 is shown. In the shown embodiment, the needle and syringe system 10 includes two primary subassemblies that are selectively joined by a healthcare

professional prior to use. The primary subassemblies include a head subassembly 12 and a syringe

subassembly 14. The head subassembly 12 mechanically engages the syringe subassembly 14 with a mechanical connection, as is later explained. Accordingly, different head subassemblies can be selectively attached to different syringe subassemblies

according to the needs of the healthcare

professional .

The syringe subassembly 14 includes a syringe barrel 16 and a plunger rod 18 that extends into the syringe barrel 16. The plunger rod 18 has a first end 20 and an opposite second end 21. The first end 20 extends into the syringe barrel 16. The second end 21 terminates with a thumb pad 22 that is used to manually move the plunger rod 18 in the syringe barrel 16 between a fully advanced first position and a fully retracted second position. The first end 20 of the plunger rod 18 is terminated with an elastomeric piston head 24. The piston head 24 is annular in shape and seals the plunger rod 18 with the interior of the syringe barrel 16.

A blind bore 26 is formed in the plunger rod 18, wherein the bling bore 26 is open at the first end 20 of the plunger rod 18. The annular shape of the piston head 24 prevents the piston head 24 from blocking access to the blind bore 26 from within the syringe barrel 16. The blind bore 26 extends for a first length into the plunger rod 18.

An elongated plug 28 is provided. The elongated plug 28 has the same length as the bore blind 26 in the plunger rod 18 and is capable of being fully received within the blind bore 26 of the plunger rod

18. Although the elongated plug 28 moves between the head subassembly 12 and the syringe subassembly 14, the elongated plug 28 is initially packaged as part of the head subassembly 12, as will later be

explained. The head subassembly 12 holds a needle 30. The needle 30 extends forward from a plastic needle base 32. The needle base 32 contains a collar 34 that is sized and shaped to engage the syringe subassembly 14. The collar 34 engages the syringe barrel 16 with a mechanical connection, such as a threaded connection or a bayonet connection. This enables a healthcare professional to be able to manually connect and disconnect the head subassembly

12 and the syringe subassembly 14. A central post 36 is concentrically disposed within the collar 34. A cylindrical cavity 38 separates the collar 34 from the central post 36. The needle 30 extends into and through the central post 36. Since the needle 30 is attached to the central post 36, the central post 36 is attached to the collar 34, and the collar 34 is attached to the syringe barrel 16, there is no relative movement between the needle 30 and the syringe barrel 16 during the operation of the needle and syringe system 10.

A tubular spacer 40 is provided as part of the head subassembly 12. The tubular spacer 40 is positioned in the cylindrical cavity 38 between the central post 36 and the collar 34. The tubular spacer 40 defines a central conduit 42 that receives the central post 36 of the needle base 32. The length of the cylindrical cavity 38 in the tubular spacer 40 is exactly the same as the length of the central post 36. The tubular spacer 40 is separate from the needle base 32 and is free to slide along the length of the central post 36.

A safety sheath 44 is provided that surrounds part of the needle 30. The safety sheath 44 is attached to an actuator cap 46. The actuator cap 46 is sized to extend over the exterior of the needle base 32. The actuator cap 46 can reciprocally move along the exterior of the needle base 32. The

actuator cap 46 can be selectively locked and

unlocked using a mechanical release 48 that is accessible on the exterior of the syringe

subassembly 14. It will therefore be understood that the actuator cap 46 can be selectively released and moved relative to the needle 30 and the needle base 32.

Referring to Fig. 4 in conjunction with Fig. 2 and Fig. 3, it can be seen that prior to use, the elongated plug 28 is part of the head subassembly 12. The elongated plug 28 is positioned within the central conduit 42 of the tubular spacer 40. This blocks the needle 30 and isolates the needle 30 within the head subassembly 12 as the head

subassembly 12 and the syringe subassembly 14 are interconnected. Once the head subassembly 12 is attached to the syringe barrel 16, the loading of the needle and syringe system 10 can begin. To load the needle and syringe system 10, the plunger rod 18 is advanced into the syringe barrel 16. As the first end 20 of the plunger rod 18 moves toward the head subassembly 12, the first end 20 contacts the elongated plug 28. The elongated plug 28 enters the blind bore 26 in the plunger rod 18. The blind bore 26 receives and retains the elongated plug 28 with an interference fit.

Referring to Fig. 5 in conjunction with Fig. 4, it can be seen that after the elongated plug 28 is received into the blind bore 26, the plunger rod 18 is retracted. The plunger rod 18 retains the elongated plug 28 and pulls the elongated plug 28 out of the tubular spacer 40. This clears the needle 30 and enables fluid to be drawn into the syringe barrel 16 through the needle 30.

Referring to Fig. 6 and Fig. 7, it can be seen that after the needle and syringe assembly 10 is filled, the plunger rod 18 is manually advanced into the syringe barrel 16. The liquid previously drawn into the syringe barrel 16 is displaced through the needle 30. As the piston head 24 advances toward the head subassembly 12, the piston head 24 presses the tubular spacer 40 into the cylindrical cavity 38 around the central post 36 of the needle base 32. Simultaneously, the elongated plug 28 is pressed into the blind bore 26 in the plunger rod 18. As the piston head 24 contacts the central post 36, the tubular spacer 40 completely fills the cylindrical cavity 38. All liquid is displaced from the syringe barrel 16 except for the exceedingly small volume that remains inside the needle 30.

As the tubular spacer 40 is pressed forward by the advancing plunger rod 18, the tubular spacer 40 moves the actuator cap 46 forward relative the needle base 32. As the actuator cap 46 moves forward, the safety sheath 44 also moves forward, wherein the safety sheath 44 covers the tip of the needle 30. As a consequence, the needle 30 is shielded and

rendered harmless just as the syringe barrel 16 empties .

It will be understood that the embodiment of the present invention that is illustrated and

described is merely exemplary and that a person skilled in the art can make many variations to that embodiment. All such embodiments are intended to be included within the scope of the present invention as defined by the appended claims .