FIELD OF THE INVENTION

The present invention relates to syringes, including syringes used for medical and industrial purposes.

BACKGROUND OF THE INVENTION

Syringes have remained basically unchanged for many years, and typically are formed of a barrel having an open end and an almost closed end, terminating in a needle hub, for supporting, when required, a needle, such as a hypodermic needle. A plunger may have a rubber bulb at one end, for insertion into the barrel, and for forming a seal with the interior of the barrel, or, alternatively, the front end of the plunger may be molded so as to perform the function of the rubber bulb. At an end protruding from the open end of the barrel, the plunger defines a thumb rest, via which pressure is applied axially along the plunger, thereby to cause depression of the plunger within the barrel, and dispensing of a liquid which may be confined between the front end of the plunger and the needle hub end ofthe barrel, through an opening in the needle hub, and, if used, through the needle.

A typical syringe normally has a linear scale provided thereon, so as to enable visual determination ofthe volume of liquid held in the barrel, and which, by complete depression ofthe plunger, is dispensed in its entirety from the syringe.

A disadvantage of the above-described syringe is that, as the dosage of volume of liquid in the syringe is determined visually, that is, by aligning the bulb with a selected scale marking, it is insufficiently precise, particularly when great accuracy is required. While an error of, for example, ±0.1 ml may not be significant as a proportion of a relatively large dose, such as, of 10 ml, in which an error of 0.1 ml is a mere 1%) this is certainly not the case in a small dose of 1 ml or less, in which an error of 0.1 ml is 10% or more, and is very significant. Accordingly, while, for the most part, 'visual dosing' by use ofthe scale provide on the side ofthe barrel is sufficient, there remain many cases in which the error inherent in visual dosing can have very serious consequences for a patient being treated with very small, concentrated doses of a medication.

This is the situation, for example, when dispensing insulin. In this case, in order to obtain higher accuracy, a syringe having a thinner barrel is used. Accordingly, each scale interval represents a smaller increment, and thus the accuracy of the visual dosing is increased. This has the disadvantage, however, of rendering the dose that can be administered by use of this syringe much smaller than other, wider syringes, and thus limits its usefulness.

In an attempt to solve the problem of dosing accuracy, there have been developed syringes such as described in US Patents Nos. 5,220,948 and 5,300,041. The '948 patent describes a syringe having a special dosing mechanism which provides high medication dose accuracy when filling the syringe. The '041 patent describes a syringe having a dose programming assembly, which is intended to provide precise multiple repetition of a selected dose for multiple injections.

While both of these syringes may indeed achieve the aim of providing accurate dosing which is not achievable in other known syringes, they both constitute complicated mechanism which are formed from a large number of precision components, and which thus markedly increases the cost of a syringe. Furthermore, as these syringes are fairly complicated, they require skills which exceed those required for use of a conventional syringe.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved syringe, which is highly accurate at small doses and easy to use, and thereby overcomes disadvantages of known art.

There is thus provided, in accordance with a preferred embodiment ofthe invention, an improved syringe which includes a cylindrical barrel having a longitudinal axis, and having a rear end and a front end, the barrel having a rear opening at the rear end, and a front opening, through which a liquid may be dispensed from the interior of the barrel, at the front end; a plunger for axial movement within the barrel, and having a front end for insertion into the barrel through the rear opening thereof, and for pressurizing liquid confined in the barrel between the front end of the plunger and the front end of the barrel, thereby to cause dispensing of the liquid through the second opening, the plunger also

having a rear end; and dosing apparatus, disposed between the rear end of the barrel and the plunger.

The dosing apparatus includes indexing apparatus defining a plurality of predetermined indexing positions at each of which axial travel of the plunger within the barrel toward the second end thereof is limited to a predetermined depth, each the depth at each the indexing position corresponding to a predetermined volume of liquid confined between the front end of the plunger and the front end of the barrel; and dosage selection apparatus for selectably engaging any of the predetermined indexing positions corresponding to a selected dosage, and for permitting filling ofthe barrel with the selected dosage only.

Additionally in accordance with a preferred embodiment ofthe invention, the dosing apparatus further includes, at each the indexing position, a stop surface located at a predetermined position with respect to the longitudinal axis, each the stop surface being located so as to correspond to a predetermined dosage; and the dosage selection apparatus includes a selector member which, in response to a relative axial motion between the plunger and the barrel which causes insertion of the plunger into the barrel, is operative to prevent insertion of the plunger into the barrel beyond a predetermined depth, corresponding to the predetermined dosage at the indexing position.

Further in accordance with a preferred embodiment of the invention, the plurality of predetermined indexing positions are spaced about the longitudinal axis, such that rotation of the plunger about the axis while inserted in the barrel causes the selector member to be brought into registration with each the indexing position, whereat a predetermined dosage may be selected in accordance with the rotational position ofthe plunger.

Additionally in accordance with a preferred embodiment of the invention, the stop surfaces are located along a helical path, and may be: discrete stop surfaces; formed transversely to the longitudinal axis and connected to adjacent stop surfaces in stepped configuration; portions of a smooth helical curve.

Further in accordance with a preferred embodiment of the invention, the stop surfaces are formed transversely to the longitudinal axis, and is operative to prevent movement therepast ofthe selector member.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which:

Fig. IA is a side view illustration of a dosing syringe constructed and operative in accordance with a first embodiment ofthe invention, in which a dosage selector member is formed on the syringe plunger;

Fig. IB is a longitudinal cross-section of the syringe of Fig. IA, taken along line B- B therein;

Fig. IC is a lateral cross-section of the syringe of Figs. IA and IB, taken along line C-C in Fig. IB, and showing a helical, indented, indexing surface formed on a rear end of the syringe barrel;

Fig. 2A is a side view illustration of a dosing syringe constructed and operative in accordance with a second embodiment ofthe invention, in which a dosage selector member is formed on the syringe plunger;

Fig. 2B is a longitudinal cross-section of the syringe of Fig. 2A, taken along line B- B therein;

Fig. 2C is a lateral cross-section of the syringe of Figs. 2A and 2B, taken along line C-C in Fig. 2B, and showing a smooth, helical, indexing surface formed on a rear end ofthe syringe barrel;

Fig. 3 A is a side view illustration of a dosing syringe constructed and operative in accordance with a third embodiment ofthe invention, in which a dosage selector member is formed on the syringe plunger;

Fig. 3B is a lateral cross-section of the syringe of Fig. 3A, taken along line B-B therein;

Fig. 3C is a side view of a helical, stepped, indexing surface formed on a rear end of the syringe barrel, shown in a two-dimensional projection;

Fig. 4A is a longitudinal cross-section ofthe syringe of Fig. 3 A, taken along line 4-4 therein, and wherein the plunger and dosage selector member are shown in a zero dosage position;

Fig. 4B is a longitudinal cross-section ofthe syringe of Fig. 3 A, taken along line 4-4 therein, and wherein the plunger and dosage selector member are shown in a maximum metered dosage position;

Fig. 5 A is a side view illustration of a dosing syringe similar to that of Figs. 3A-3C, but wherein the stepped index surface is symmetrical, such that each index location - with the exception ofthe zero and maximum positions - occurs twice;

Fig. 5B is a side view of the indexing surface of Fig. 5 A, shown in a two- dimensional projection;

Fig. 6A is a side view illustration of a dosing syringe constructed and operative in accordance with a fourth embodiment of the invention, in which a dosage selector member is formed on the syringe plunger, and having an indexing surface formed interiorly of the barrel;

Fig. 6B is a lateral cross-section of the syringe of Fig. 3 A, taken along line B-B therein;

Fig. 6C is a partially cut-away side view ofthe syringe barrel seen in Fig. 6 A, and in which there is provided a stepped index surface, similar to that of Figs. 5A and 5B, but formed as a ledge inside the barrel;

Fig. 7A is a side-sectional view of a syringe, constructed in accordance with a sixth embodiment of the invention, in which each index position is defined as a longitudinal groove formed interiorly ofthe barrel;

Fig. 7B is a partial end view ofthe syringe of Fig. 7 A, taken along line B-B therein;

Fig. 7C is an enlarged detailed view of a rear end position of the barrel of the syringe of Fig. 7 A, showing the indexing grooves thereof;

Fig. 7D is a diagrammatic view of the indexing surface of the embodiment of Figs. 7A-7C, shown in a two-dimensional projection; and

Figs. 8A and 8B are respective side-sectional and lateral cross-sectional views of a syringe constructed according to a seventh embodiment ofthe invention, in which a dosage selector member is formed on an interior surface ofthe barrel, and each indexing position is defined by an indexing groove formed on the plunger.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to Figs. 1A-1C, there is shown a dosing syringe, referenced generally 10, which is constructed and operative in accordance with a first embodiment of the invention. Syringe 10 is constructed, as are the syringes 200-800 shown and described below in conjunction with Figs. 2A-8B, so as to easily enable highly accurate dosing of liquid medications and other liquids, both in small and large doses. In general, syringe 10 is formed of a cylindrical barrel 12 having a longitudinal axis 14, a plunger 16, and dosing apparatus, referenced generally 18.

Barrel 12 has a rear end 20 defining a rear end opening 22, having a diameter substantially equal to that of the barrel 12, and a front end 24, which defines a needle hub 26 to which a hypodermic needle (not shown) may be attached, if required. Needle hub 26 defines a bore 30, which enables dispensing from the interior ofthe barrel 12 to the exterior thereof.

Plunger 16 is arranged for axial movement within barrel 12 and has a front end 32 which, as in the present example, may have attached thereto a rubber bulb 34 (Fig. IB), and which is insertable into barrel 12 through rear opening 22, and which may further be moved axially between the rear end 20 and front end 24, as shown in Figs. IA and IB. Alternatively, front end 32 of plunger 16 may be molded so as to fulfill the functions of bulb 24, thereby obviating the need for use thereof. Although the examples shown and described in conjunction with drawings include use of a rubber bulb, this is by way of example only, and the syringes ofthe invention include both two-part plungers employing a rubber bulb at the front end, and one-part plungers, having a molded front tip.

In use, barrel 12 contains the maximum volume of fluid when plunger 12 is at its rear most position with respect to the barrel, and is, by definition, empty, once plunger 16 has been completely inserted into the barrel 12, such that bulb 34 engages front end 24 of the barrel. Plunger 16 further has a rear end thumb rest 36, which, when used in conjunction with finger flange 38 formed at the rear end 24 of the barrel 24, is used to apply axial pressure to the plunger, typically by use of the thumb of a user, which acts to pressurize liquid confined between the barrel front end 14 and bulb 34, thereby to cause it to be dispensed from the barrel via bore 30 formed in needle hub 26.

The present invention is characterized by the provision of novel dosing apparatus 18 which, as will be appreciated from the description that follows, enables simple and

convenient very highly accurate measurement of small doses. Dosing apparatus 18 is provided at a common interface between the barrel rear end 20 and the plunger 16, and is operative to enable selection of a desired, typically small dosage, and filling of barrel 12 therewith.

More particularly, the dosing apparatus 18 defines a plurality of indexing positions, referenced 40, defined in the present embodiment by notches 41, at each of which axial travel of plunger 16 within barrel 12 toward the front end 24 thereof is limited to a predetermined depth, wherein each different predetermined depth at each indexing position 40 corresponds to a predetermined selectable volume of injectable liquid confined between bulb 34 and barrel front end 24. There is also provided a dosage selector member 42, which cooperates with the indexing notches 41 so as to limit the depth of insertion of plunger 16 into barrel 12.

It is seen that indexing notches 41 are formed on a generally helical rear edge 44 or indexing surface of barrel 12, and are provided at volumetric intervals of 0.1 ml, and selector member 42 is formed as an elongate rib on plunger 16.

As described above in the Background of the Invention, the principal necessity for highly accurate dosing, to levels of, for example, ±0.1 ml, exists at very small doses, such as when the error should not be allowed to exceed a predetermined proportion, typically 5- 25% of the entire dosage. For greater doses, such high accuracy is generally not required, and so it will normally not be necessary to provide the novel dosing apparatus of the invention for doses considerably in excess of 1.0 or 1.1 ml. Generally, for doses exceeding this range, 'visual dosing' will be sufficiently accurate, and so a suitable prior at scale, referenced 46 (Fig. IA), is provided in addition to dosing apparatus 18.

Notwithstanding the examples of 1.0 and 1.1 ml ofthe maximum dosages for which the dosing apparatus ofthe invention may be required, these ranges are clearly for example only, and the present invention includes any dosage for which it may be sought to construct a syringe in accordance with the principles ofthe present invention.

Use ofthe syringe 10 is as follows:

Initially, plunger 16 is rotated until dosage selector member 42 is brought into alignment with the indexing position corresponding to a dose of 0.0 ml, as seen in Fig. IA. Plunger 16 is then inserted completely into barrel 12 such that dosage selector member 42

fully engages the notch 41 at the 0.0 ml (empty) index position. A needle (not shown), attached to needle hub 26 is inserted into a source of liquid preparation. While retaining the needle in the liquid source, plunger 16 is extended such that, due to a seal existing between rubber bulb 34 and the interior of barrel 12, the liquid is drawn into the space formed in the barrel 12 between its front end 24 and bulb 34. Plunger 16 is then extended until it can be rotated so as to bring the selector member 42 into alignment with the indexing position corresponding to a selected dose, for example, of 0.2 ml. It is evident that in order to bring plunger 16 into the desired position, a volume of greater than that required is drawn into the barrel 12.

Accordingly, once plunger 16 has been sufficiently extended, and then rotated so as to align selector member 42 with the 0.2 ml indexing position, plunger 16 is once again inserted into the barrel until selector member 42 is prevented from further insertion, as it engages the notch 41 at the selected 0.2 ml position.

It will thus be appreciated that a selected small dosage can be measured, as described, without having to depend on the visual skill and dexterity of an operator but, instead, by depending solely on the unique indexing position corresponding to each dosage.

Referring now generally to Figs. 2A-8B, there are provided, as mentioned above, syringes, respectively referenced 200-800, which are constructed according to alternative embodiments of the present invention. Accordingly, for the purposes of conciseness and clarity, syringes 200-800 (Figs. 2A-8B) are described below with respect only to the differences which exist between each of these embodiments and that of Figs. lA-lC. Furthermore, all portions of syringes 200-800 having counteφart portions which have been shown and described above in conjunction with syringe 10 (Figs, 1A-1C), are indicated in Figs. 2A-8B by similar reference numerals, but with an additional single digit prefix in accordance with the drawing number, such that all portions of syringe 200 (Figs. 2A-2C) corresponding to similar portions of syringe 10, are denoted by the prefix "2", those of syringe 300 (Figs. 3A-3C) are denoted by the prefix "3", and so on.

Referring now to Figs. 2A, 2B and 2C, in the illustrated embodiment of the invention, dosing apparatus 218 is defined by a generally smooth, helical rear indexing surface 244 and, in place of rear-facing notches 41 of syringe 10 (Figs. 1A-1C), the barrel rear end 220 defines a plurality of inward-facing grooves 241, seen in Fig. 2C, which cooperates with selector member 242, formed as a radially extending rib on plunger 216. At

least selector member 242 - and preferably the entire plunger 216 - is formed from a resilient material that enables rotation of plunger 216 between indexing positions. It is seen that a visual scale of typically 0.0-1.0 ml is provided on a rear edge 239 of finger flange 238 of barrel 212, thereby to indicate the volumetric capacity ofthe barrel 212 at each indexing position.

Use ofthe syringe 200 is similar to that of syringe 10 described above in conjunction with Figs. 1A-1C, except that the mechanical registration between plunger 216 and barrel 212 is provided by engagement of a radially outward-facing edge 243' of selector member 242 with selected indexing grooves 241, while control ofthe depth of plunger 216 in barrel 212 is provided by engagement of a front edge surface 243" of selector member 242 with helical indexing surface 244.

Referring now to Figs. 3 A, 3B and 3C, in the illustrated embodiment of the invention, dosing apparatus 318 is similar to dosing apparatus 218, shown and described above in conjunction with Figs. 2A, 2B and 2C, except that, in the present embodiment, helical indexing surface 344 is a stepped surface, seen in projected view in Fig. 3C. It is seen that, each indexing position, in addition to inward-facing grooves 341, seen in Fig. 3B, is also defined by an index surface 344' formed at right angles to axis 314. It is also seen that a visual scale of typically 0.0-1.1 ml may be provided on barrel 316 adjacent to its rear end 320. It is further seen, by referring to Fig. 3B, that, in addition to selector member 342 which, in the present embodiment is provided as a laterally extending protrusion or tooth, all ofthe web portions 350 of plunger 316 may be extended radially outward adjacent to the thumb rest end thereof, such that they all engage indexing grooves 341.

Referring now also to Figs. 4 A and 4B, the plunger 316 of syringe 300 is shown, respectively, in a zero dosage position, whereat bulb 334 is in touching contact with front end 324 of barrel 312; and in a maximum metered dosage position, in which dosage selector member 342 is seen to be engaging the uppermost stepped index surface 344', corresponding to a dosage of 1.1 ml.

It is furthermore seen that, in the present embodiment, plunger 316 may be formed so as to have web portions 350 in which are formed a plurality of openings 352. It will be appreciated that the presence of these openings imparts increased flexibility to the plunger 316, thereby to reduce the mechanical wear on the plunger as it is rotated between different indexing positions. It will, of course, be appreciated, that, instead of or in addition to the

provision of openings 352, plunger 316 may be formed with thin wall sections, thereby to impart a desired flexibility to the plunger.

Referring now to Figs. 5 A and 5B, syringe 500 has dosing apparatus 518 which is similar is similar to dosing apparatus 318, shown and described above in conjunction with Figs. 3A-3C, except that, in the present embodiment, stepped helical indexing surface 544 is symmetrical, thereby to define two index surfaces 544' formed symmetrically with respect both to the maximum metered dose indexing position, exemplified herein as 1.0 ml, and to the empty or 0.0 ml indexing position.

Referring now to Figs. 6A, 6B and 6C, in the illustrated embodiment of the invention, dosing apparatus 618 is generally similar to dosing apparatus 518, shown and described above in conjunction with Figs. 5A and 5B, in as much as the helical indexing surface 644, seen most clearly in Figs. 6B and 6C, is also a symmetrical stepped surface. In the present embodiment, however, instead of being formed as a rearmost edge ofthe barrel, as in syringe 500, the stepped indexing surface 644 is defined by an interior ledge or shoulder, caused by a widening of rear end 620 of barrel 612. The remainder of the construction of syringe 600, including barrel 612 and plunger 616, is similar to that of syringe 500, except that, in the present embodiment, a metered dose scale, referenced 660, is seen to be provided on the interior of barrel 612 adjacent to the front end 624 thereof. An indication of the volume at each indexing position 640 is provided by a line indication 662 provided by way of example only, adjacent to front end 632 of plunger 616.

Referring now to Figs. 7A-7D, the illustrated syringe, referenced generally 700, is generally similar to syringe 600, shown and described above in conjunction with Figs. 6A- 6C, except for the dosing apparatus 718. In the present embodiment, dosing apparatus is formed of a plurality of indexing grooves 741, each of which is a different length, and defines a different indexing position 740. Dosage selector 742 is provided in the form of a radially extending protrusion, and is operative to travel along a selected indexing groove 741, and to engage an end surface 744' of that groove, such that the depth of entry of plunger 716 into barrel 712 is controlled by the depth of end surface 744' of the indexing groove 741. It is thus seen that, when taken together, the plurality of end surfaces 744' combine to define a generally helical, stepped, rear-facing indexing surface 744, similar to the various indexing surfaces 44, 244, 344, 544 and 644, shown and described above in conjunction with Figs. 1 A-6C.

In similar fashion to the embodiment of Figs. 6A-6C, there is provided a scale 760 and a line indication 762 which together serve to indicate the metered dosage at any given rotational position of plunger 716 relative to barrel 712.

It is further seen that, as opposed to the embodiments of the invention shown and described above in conjunction with Figs. 1A-6C, in which the incremental dosage interval between adjacent metered dosages is 0.1 ml, in the present embodiment, the interval varies from 0.05 ml for the smallest doses, for which the proportional by even a small amount may be very large, to 0.1 ml, as in other embodiments of the invention; the maximum metered dosage being 1.5 ml. It will thus be appreciated that, in a syringe constructed in accordance with the present invention, as the accuracy of the metered dosages depends not on the visual skilled and dexterity ofthe user, but on the accuracy of the manufacturing process of the syringe, substantially any predetermined dosage interval and any predetermined maximum metered dosage can be provided, as required.

Referring generally to Figs. 1A-7D, it is seen that the indexing notches or grooves (41, 241, 341, 541, 641 and 741) and helical indexing surface (44, 244, 344, 544, 644 and 744) are formed at the rear end of the syringe barrel, and cooperate with the selector member (42, 242, 342, 542, 642 and 742) which is formed on the plunger so as to be outward-facing, and so as to be engageable with the notches or grooves and indexing surface.

Referring now to Figs. 8A and 8B, however, it will be appreciated that, in accordance with yet a further embodiment of the invention, the dosing apparatus 818 of syringe 800 may be provided with a plurality of indexing grooves 841 formed on plunger 816, and selector member 842 may be provided as an inward-facing protrusion formed on the interior of barrel 812. Grooves 841 are formed so as to have different depths, thereby to define a forward-facing, helical indexing surface 844, which is represented by an imaginary line connecting the closed ends 844' of grooves 841. It will be appreciated that use of the syringe 800 is analogous to the use of any of the other syringes 10, 20, 300, 500, 600 or 700, and thus does not need to be described herein.

It will be appreciated by persons skilled in the art the scope ofthe present invention is not limited by what has been particularly shown and described above. Rather, the scope ofthe invention is limited solely by the claims, which follow.