BACKGROUND OF THE INVENTION Potentially lethal infections such as human immune deficiency virus (HIV), hepatitis B, or the like, can be transferred by needle sticks from needles of used catheter infusion and fluid extraction assemblies. The risk of needle stick extends to medical practitioners, persons responsible for handling equipment used in these procedures after use, and the like.

There is a need for a safety IV catheter assembly that can be manufactured at low cost, which will permit single handed safe rendering of the needle, and which will not require a significant deviation from operating procedures with which medical personnel are familiar and comfortable.

SUMMARY OF THE INVENTION According to the invention there is provided a safety IV catheter assembly, which includes : a chamber body defining a flash chamber and at least two guard receiving formations; a hollow needle attached to the chamber body, and defining a point and an internal passage leading longitudinally from the point to the flash chamber; and a needle guard, wherein the needle guard includes at least two elongate limbs, slideably receivable in the guard receiving formations, so that the needle guard and the chamber body are slideable relative to each other between an operable condition in which the point extends beyond the needle guard, and a safe condition in which the guard surrounds the needle.

The needle guard may include catheter receiving means, to which a catheter is removably attachable, coaxially with the needle. The catheter receiving means may be integrally formed with the limbs, which may extend from the catheter receiving means, or the catheter receiving means may be releasably or non-releasably attachable to the limbs of the needle guard.

The catheter receiving means may include a hollow spigot on which the catheter is removably attachable, and the assembly may include an IV over-the-needle catheter, removably attached on the spigot. The IV catheter may include a hub removably attachable on the spigot so that the needle is sheathed in the catheter, when the assembly is in the operable condition, allowing the needle and catheter to penetrate a patient's vein.

The point of the needle may be disposed within the hollow spigot when the assembly is in the safe condition, and may extend through the hollow spigot when the assembly is in the operable condition, so that the spigot forms a finger barrier, preventing needle stick into a user's finger by the needle point.

The limbs of the needle guard may comprise a pair of elongate rails, connected in a generally parallel, spaced arrangement by a spacer plate, disposed at a rear end of the needle guard, and by a spigot formation disposed at a front end of the needle guard.

The needle guard may include slide stop means, disposed to limit sliding of the needle guard from the operable to the safe condition, up to a point where the needle point is protected within the spigot. The spacer plate may define the slide stop means.

The spacer plate and/or the spigot formation may be formed integrally with the slide rails. Alternatively, either or both of the spacer plate and spigot formation may be formed separately from, and then affixed to, the rails, for ease of forming the needle guard and assembling the catheter assembly.

The needle guard may include a finger tab which may extend from the spigot formation, to allow the needle guard to be held stationary while the chamber body is moved relative to the needle guard along the limbs, to retract the needle through the spigot until the chamber body abuts the slide stop means, the point of the needle is protected within the bore of the spigot, and the assembly is in the safe condition.

The spigot may include a plug of absorbent material, such as a non-pyrogenic open cell foam, disposed within the bore of the spigot to provide sweeping means for wiping an outside of the needle when the needle is being moved together with the chamber body, relative to the spigot. The bore of the spigot may include a rear part of increased diameter, in which the plug is receivable. The plug may be disposed so that it closes around the point of the needle, when the assembly is in the safe condition, to absorb blood spilt from the point of the needle, and to prevent backflow of blood from the catheter, through the needle, towards the flash chamber.

The assembly may include locking means for locking the needle guard and the chamber body relative to each other in the safe condition, to allow safe disposal of the assembly after use. The locking means may be non-releasably lockable and may include at least one pawl, extending from the chamber body and being disposed to engage a first complementary receiving formation, defined on the needle guard, to lock the needle guard non-releasably in the safe condition.

The assembly may include releasable locking means for locking the needle guard and chamber body relative to each other in the operable position, to avoid accidental premature retraction of the needle out of the catheter. The releasable locking means may include at least one pawl extending from the chamber body and a second complementary receiving formation, defined on the needle guard, spaced from the first receiving formation, in the direction of the spigot. The first and second receiving formations may each be in the form of a recess defined in the needle guard.

At least one groove may be defined in the needle guard, extending between a first receiving formation and a second receiving formation, so that a pawl can slide partly within the groove.

The assembly may include a shield, which can be removably fitted over the needle and catheter when in the operable condition. The shield may include releasable attachment means for releasably engaging with the chamber body, when the assembly is in the operable condition, e. g. prior to use.

The assembly may include a cap releasably attachable to the needle guard, to receive the point of the needle in a recess defined within the cap, when the assembly is in a pre-use condition, wherein the needle guard surrounds a substantial length of the needle, the substantial length of the needle being less than that which is surrounded by the needle guard when the assembly is in the safe condition.

The cap may be releasably attached to the needle guard by being received in a spigot engaging formation, and a spigot formation may be releasably attachable to the chamber body, when in the pre-use condition, so that the cap is displaceable by the spigot formation, which in turn is lockingly receivable in the spigot engaging formation, when the chamber body is moved from its pre-use position to its operable position.

The cap and the spigot formation may be of similar shape and dimensions, and may each comprise two parts, hingedly connected in clam- shell-fashion.

The assembly may include releasable locking means for locking the chamber body and the needle guard in the pre-use condition, to hold the chamber body and needle guard against sliding relative to each other.

The chamber body may include venting means disposed between the flash chamber and an outside of the body, to allow gas to be vented from the flash chamber. The venting means may include an air- permeable plug formation disposed in a rear of the chamber. The body may include chamber sealing means to prevent accidental dislodgement of the plug formation. The spacer plate may form the chamber sealing means, by being receivable in a complemental recess defined in a rear face of the body, to close a rear opening of the flash chamber, when the assembly is in the safe condition. The spacer plate may include a plug formation, receivable in a rear opening of the flash chamber, when the assembly is in the safe condition.

The chamber body and needle guard may be configured to allow reciprocal sliding of the chamber body along the limbs, or to allow sliding only in the direction from the operable condition to the safe condition.

The components of the catheter assembly may be moulded in one or a selection of different plastics. Typically, the chamber body may be moulded in a translucent plastic such as polycarbonate, or in a suitable grade of translucent polypropylene, thereby enabling the practitioner to view blood- flash in the chamber as an indication that the catheter is correctly emplaced in the patient's vein, before the needle is retracted therefrom.

The invention will now be described, by way of non-limiting example, with reference to the accompanying diagrammatic drawings: BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: Figure 1 shows a three-dimensional view of a safety IV catheter assembly in accordance with a first embodiment of the invention, in an operable condition, prior to use; Figure 2 shows a three-dimensional view of the catheter assembly of Figure 1, with its shield removed; Figure 3 shows a cross-sectional side view of the catheter assembly of Figure 2, taken at lil-lil ; Figure 4 shows a detail cross-sectional top view of part of the catheter assembly of Figure 1, taken at IV-IV ; Figure 5 shows the cross-sectional top view of part of the catheter assembly of Figure 4 with its shield removed; Figures 6 shows a three-dimensional, schematically transparent view of the catheter assembly of Figure 2 in a safe condition; Figures 7 and 8 show detailed three-dimensional views of parts of the catheter assembly of Figure 6; Figure 9 shows a cross-sectional top view of part of the catheter assembly of Figure 6, taken at IX-IX ; Figure 10 shows a rear three-dimensional view of a chamber body of the catheter assembly of Figures 1 to 9; Figures 11,12 and 13 show cross-sectional side views of a safety IV catheter assembly in accordance with a second embodiment of the invention in a pre-use condition; in an operable condition; and in a safe condition, respectively; Figures 14A, 14B and 14C show a top plan view, a rear elevational view, and an assembly detail view, respectively, of a separate spigot and/or cap of the catheter assembly of Figures 11 to 13; Figure 15 shows a three-dimensional view of a safety IV catheter assembly in accordance with a third embodiment of the invention, in an operable condition, prior to use; Figure 16 shows a three-dimensional view of the catheter assembly of Figure 15, with its shield removed; Figure 17 shows a three-dimensional view of the catheter assembly of Figure 15, midway between the operable condition and the safe condition; and Figure 18 shows the catheter assembly of Figure 15 in the safe condition, with the catheter removed.

DETAIL DESCRIPTION OF THE DRAWINGS Referring to Figures 1 to 10 of the drawings, in a first embodiment of the invention a safety IV catheter assembly is generally indicated by reference numeral 10 and includes a transparent, elongate, rectangular tubular chamber body 12, slideably attached to an elongate needle guard assembly 14 comprising a pair of limbs in the form of equi- distantly-spaced vertical slide rails 16. Each of the slide rails 16 has a front end 18 (as illustrated in Figure 4), defined by a spigot formation 20 and a rear end 22 including slide stop means in the form of a spacer plate 24 formed integrally with the rails 16.

In an operable condition of the catheter assembly 10 illustrated in Figures 2 and 3, the hub 26 of an IV catheter 28 is detachably mounted on the spigot 30 of the spigot formation 20 with a needle 32 sheathed within the catheter 28, such that the point 34 of the needle 32 extends marginally beyond the front end 36 of the catheter 28. An absorbent foam plug 31 is held captive in a rear part 21 of a bore of the spigot formation 20, so as to close circumferentially around the needle 32 while the catheter assembly 10 is in the operable condition.

A rear end 38 of the needle 32 is seated in a needle seat 40 in a front face 42 of the chamber body 12 and extends rearwardly into a flash chamber 44 in such manner that blood-flash 46 emitted from the rear end 38 of the needle can be clearly seen in the chamber 44 as an indication that the catheter 28 has been correctly emplaced in a patient's vein (not shown). A fairlead 41 is provided in the front of the needle seat 40 to guide the rear end 38 of the needle 32 into a press fit engagement with the needle seat 40.

An air-permeable/fluid-impermeable plug formation 47 is push-fitted into the rear opening of the flash chamber 44 so that back-flow of blood into the chamber 44 is contained within the chamber 44 but not impeded by a build up of air pressure therein.

A finger tab 48 is provided on the spigot formation 20 with which to urge the needle guard assembly 14 forwardly relative to the chamber body 12 and thus to thread the catheter 28 off the needle 32 during emplacement of the catheter 28 in a patient's vein (not illustrated).

A needle shield 50 is provided with releasable attachment means defined by a detachable clipping arrangement 52 acting in cooperation with the chamber body 12 as shown in Figure 4, so as to protect the needle 32 and catheter 28 assembly in the operable condition of the assembly of Figure 1, prior to use. The clipping arrangement 52 includes a partial annular groove 54 extending circumferentially around a portion of an inner wall of the needle shield 50 proximate its rear open end 56, the groove 54 being urged in detachable locking engagement over a complemental protuberance 58 disposed near a front of each external side face 60 of the chamber body 12.

Figure 5 shows the part of the catheter assembly 10 as illustrated in Figure 4, in the operable condition, with the needle shield 50 removed. An inwardly-biased clip pawl 62 defining a locking formation at a front end of each side face 60 of the chamber body 12 is held in temporary sprung engagement in a blind backwardly tapered recess 64 defining a complemental detent formation in the front end 18 of each of the slide rails 16, immediately to the rear of a back face 66 of the spigot formation 20, while the catheter assembly 10 is in the operable condition, prior to being brought into use.

Referring to Figures 6 to 10, dotted lines are used to illustrate a schematic partially transparent view, which shows how the catheter assembly 10 operates in practice. In use, the point 34 of the needle 32 supporting the front end 36 of the catheter 28 is first introduced into a patient's vein (not shown). The finger tab 48 on the spigot formation 20 is then urged forwardly relative to the chamber body 12, thereby threading the catheter 28 off the needle 32 until it is correctly emplaced in the vein. With the hub 26 of the catheter 28 still mounted on the spigot 30, a user, i. e. a practitioner continues to move the flash chamber 12 rearwardly relative to the spigot formation 20, the slide rails 16 moving axially forwards through guard receiving formations in the form of sideways 68 defined in the chamber body 12, until the chamber body 12 is prevented from further rearward movement by the slide stop formation and spacer plate 24. At this point the clip pawls 62 defining locking formations on each side 60 of the chamber body 12 engage in locking arrangement with recessed apertures 70 (as shown in Figures 1,2, 6 and 8) defining complemental locking formations on each side rail 16. Simultaneously, the spacer plate 24 defining flash chamber sealing means is drawn into a complemental sealing recess 74 (shown in Figure 10) defined in the rear face of the chamber body 12, thereby effectively preventing accidental dislodgement of plug 47 and consequent spillage of blood 46 out of the barrel 44.

The practitioner may now safely set up the IV drip or extraction line (not shown) and at his or her convenience detach the hub 26 of the catheter 28 from the spigot 30 in order to attach the line in a familiar and conventional manner.

Figures 6, and 7, further illustrate in more detail a mounting formation 77 whereby the spigot formation 20 is non-releasably engaged with the front ends 18 of the slide rails 16 by means of inwardly projecting nibs 80 formed in sideways 82 in the spigot formation 20 over which complemental grooves 84 formed in the slide rails 16 are urged in locking engagement. The needlepoint 34 is shown in the safe condition, covered by the spigot 30.

Figure 8 shows in more detail the position of the chamber body 12 of Figure 6, when it has been fully retracted into the safe condition.

Figure 9 shows how the inwardly biased clip pawls 62 formed on the sides 60 of flash chamber 12 are drawn into non-releasable locking engagement with the recesses 70 formed in slide rails 16, when the catheter assembly 10 is in the safe condition.

Figure 10 shows a detailed rear three-dimensional view of the chamber body 12, to illustrate the sealing recess 74 formed in the rear of the chamber body 12 into which the rear spacer plate 24 of the needle guard assembly 14 (not shown) is drawn in sealing engagement, so as to prevent accidental displacement of the plug 47 and consequent spillage of blood contained in the chamber 44, when the catheter assembly 10 is in the safe condition as shown in Figures 6 to 9.

The chamber body 12 is provided with a series of finger ribs 76 on the side faces 60 of the chamber 12, to facilitate manual retraction of the chamber body 12 relative to the needle guard assembly 14.

Figures 11 to 14 show a safety IV catheter assembly in accordance with a second embodiment of the invention generally indicated by reference numeral 10.1, in which the significant moulding and material costs associated with the protective needle shield 50, are largely ameliorated by providing in its place a protective needle cap or mini-cap 78.

Referring to Figure 11, a safety catheter assembly 10.1 is shown in a stowed, needle-protected pre-use condition, in which it is sterile- packed prior to being brought into use. A chamber body 12.1 is held in a releasably locked position in like fashion to that shown in Figure 5, save only that the inwardly-biased clip pawl 62 defining a locking formation at a front end of each side face 60 of the chamber body 12 in Figure 5, is held in temporary sprung engagement in a blind backwardly tapered recess (not here illustrated) defining a complemental detent formation towards the rear end of each of the slide rails 16.1 in the embodiment shown in Figure 11.

The chamber body 12.1 is held in this releasably locked position just short of sealing engagement with the spacer plate 24, in which position it would be non-releasably locked in the safe condition shown in Figure 9.

Needle shielding means is provided by a protective needle mini-cap 78 discardably mounted in a spigot engaging formation or spigot carrier formation 80 defining the front end of a needle guard assembly 14.1.

Mounting means for mounting the mini-cap 78 to the spigot carrier formation 80 are provided by an outwardly projecting circumferential rib 82 at the rear of the mini-cap 78, which is releasably detained in a complementary groove 84 defined in a front open end of the spigot carrier formation 80. The mini- cap 78 is moulded identically to a separate spigot component 86 having chamber body mounting means 88 arranged releasably to engage complementary spigot component mounting means 90 formed in the front face 92 of the chamber body 12. 1.

The manner in which the second embodiment of the invention is used, will be described with reference to Figures 11,12 and 13. The safety catheter assembly 10.1 is removed from its sterile packaging (not illustrated) in the pre-use condition shown in Figure 11. The practitioner then urges the finger tab 48.1 backwardly which has the effect of moving the needle point 34 and catheter 28 forwardly through the front opening 94 of the mini-cap 78, until the leading edge 96 of the catheter hub 26 is brought up against the rear edge 98 of the mini-cap 78. Continued rearward movement of the finger tab 48.1 causes the catheter hub 26 to displace the mini-cap 78, which pops out of the front end of the spigot carrier formation 80, thereby allowing the catheter hub 26 to pass forwardly through the opening in the spigot carrier formation 80. The mini-cap 78 is moulded in sprung clamshell configuration, causing the clamshell to spring open as it pops out of the front end of the spigot carrier formation 80, so that the mini-cap 78 drops free of the catheter 28 and needle 32.

As the finger tab 48.1 continues to move rearwardly, the spigot carrier formation 80, as illustrated in Figure 12, is urged into locking engagement with the separate spigot component 86. Locking means for achieving this is provided by a spigot carrier locking formation 100, carried on the spigot component 86 and comprising an annular locking groove 102, which is brought into locking engagement with a spigot component locking formation 104 comprising a complementary internally projecting annular rib 106, carried on the spigot carrier formation 80.

As the finger tab 48.1 is now urged reciprocally forwardly, chamber body mounting means 88 and complementary spigot component mounting means 90 are disengaged, and from this point forward, the operation and function of the present embodiment is essentially the same as that shown in Figures 6 to 10.

Referring to Figures 14A, 14B and 14C, the clamshell configuration of needle mini-cap 78 and separate spigot component 86 is respectively shown in top plan, rear end, and assembly detail views. It will be readily appreciated that, because the components are moulded in two halves, joined by an integral hinge 108, in assembly, they can be folded around the needle 32 or catheter 28, rather than having to be threaded around either of them. It also means that when mini-cap 78 is popped out of the spigot carrier formation 80, it falls away from the catheter 28 and needle 32 rather than circumferentially embracing them. A further advantage to this moulding method in the case of separate spigot component 86, is that identical chambers 21.1 can be separately packed with absorbent foam 31.1 such that a plug of such foam is formed around the needle 32 when the clamshell halves are brought together as illustrated in Figure 14C, thereby avoiding the necessity of pushing the needle 32 through a completely pre-formed plug 31.1.

Referring finally to Figures 15,16, 17, and 18, a catheter assembly in accordance with a third embodiment of the invention is generally indicated by reference numeral 10.2.

The catheter assembly 10.2 is identical to the catheter assembly 10 shown in Figures 1 to 10 of the drawings, including a chamber body 12, needle guard 14 including two rails 16, a spigot formation 20, etc.

The only addition feature of the assembly 10.2 is that a longitudinal groove 110 is defined laterally on each rail 16, extending from a position proximate the aperture 70 to a position proximate the aperture 64 (not shown) on the same limb. When the body 12 is slid along the rails 16, the pawl 62 extends partly into the groove 110, thereby to avoid inhibiting friction, that would have resulted if the pawl 62 were to abut the rail 16.

The invention illustrated holds the advantage of reducing the risk of needle stick from catheter infusion and fluid extraction assemblies, which could lead to the transmission of infections, including potentially lethal infections such as HIV and hepatitis B viruses, while avoiding the need for equipment external to the IV catheter assembly, to render it safe. It also holds the advantage of simplicity and low cost of manufacture, since it includes few parts which are light and simple. It further holds the advantage that emission of blood from an emplaced catheter is prevented while the catheter is still mounted on the spigot, thereby affording a user time to set up an intravascular connection