Syringe Having Limited Plunger Movement

Abstract

The present invention includes a syringe having a plunger movably mounted in a hollow barrel for reciprocal movement therein in directions along its axis. A flexible elongated member has a maximum length when stretched taut and has one end affixed to the barrel and an opposite end affixed to the plunger in a manner whereby when the plunger is moved a determined distance in a predetermined direction the flexible member is stretched taut and limits further movement of the plunger in the predetermined direction. A cooperating guide device of the barrel and plunger guides the plunger in a manner which prevents it from rotation about its axis.

Parent Case Text

This application is a continuation of Ser. No. 680,172 filed Nov. 2, 1967, now abandoned.

Description

The present invention relates to a syringe having limited plunger movement. More particularly, the invention relates to a disposable syringe for charging and discharging a constant volume of fluid.

A principal object of the present invention is to provide a new and improved syringe. The syringe of the present invention has a limited plunger movement which provides charging and discharging of a constant volume of fluid. The syringe of the present invention is disposable. The syringe of the present invention automatically provides and indicates the charging and discharging of a constant volume of fluid without continuous supervision of the user. The syringe of the present invention has a plunger which is prevented from rotating about its axis. The syringe of the present invention is of simple structure and is inexpensive to manufacture. The syringe of the present invention is very easy to use and functions with efficiency, effectiveness, accuracy and reliability.

In accordance with the present invention, a syringe comprises a hollow barrel and a plunger, having an axis, movably mounted in the barrel for reciprocal movement therein in directions along its axis. A flexible elongated member has a maximum length when stretched taut and has one end affixed to the barrel and an opposite end affixed to the plunger in a manner whereby when the plunger is moved a determined distance in a predetermined direction the flexible member is stretched taut and limits further movement of the plunger in the predetermined direction.

The flexible member is a fiber or stringlike member. The barrel has an axis, a forward end portion for accommodating a hypodermic needle, a rearward open end portion through which the plunger extends from the barrel and a middle portion between the forward and rearward end portions. A flange extends from the barrel at the rearward end portion thereof substantially perpendicularly to the axis of the barrel. The barrel includes a notch formed in the rearward end thereof and the plunger includes a key protrusion extending parallel to its axis and slidably seated in and guided by the notch in a manner whereby the plunger is prevented from rotating about its axis.

A handle extends from the plunger at the free end thereof substantially perpendicularly to the axis of the plunger. One end of the flexible member is affixed to the flange and the opposite end of the flexible member is affixed to the handle.

In order that the present invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, wherein similar components are identified by the same reference numerals.

FIG. 1 is a perspective view of an embodiment of the syringe of the present invention;

FIG. 2 is a side view of the embodiment of FIG. 1;

FIG. 3 is a partially fragmented rear view, taken along the lines III-III of FIG. 2; and

FIG. 4 is a partially fragmented view, taken along the lines IV-IV of FIG. 3.

The syringe of the present invention comprises a hollow barrel 11 having an axis 12 (FIG. 2). The barrel 11 has a forward end portion 13 for accommodating a hypodermic needle 14 (shown in broken lines in FIG. 1). The forward end portion 13 includes a first conical portion 15. The first conical portion 15 terminates in a second truncated hollow conical portion 16 which has an axis of symmetry coincident with the axis 14 of the barrel 11.

The barrel 11 has a rearward open end portion 17 having a protuberance 18 (FIGS. 3 and 4) extending toward the axis 14 of said barrel. The protuberance 18 has a notch 19 (FIG. 3) formed therein. The barrel 11 also has a middle portion 21 between the forward end portion 13 and the rearward end portion 17. The middle portion 21 of the barrel 11 is integral with and communicates with the second conical portion 16.

A flange 22 extends from the barrel 11 at the rearward end portion 17 substantially perpendicularly to the axis 12 of said barrel. The flange 22 may be integrally formed with the barrel 11. The flange 22 has a substantially ovular surface 23 (FIGS. 2 and 4) coaxial with, but at a slight angle of inclination with a plane perpendicular to the axis 12 of the barrel 11. A collar 24 (FIGS. 2 and 4) extends substantially perpendicularly from the ovular surface 23 at the periphery 25 (FIGS. 1 and 3) thereof to provide a rearwardly opening recess 26 (FIGS. 2 and 4) with said ovular surface. The ovular surface 23 has a hole 27 (FIG. 4) formed therethrough.

A plunger 28 has an axis 29 (FIG. 4) and is movably mounted in the barrel 11 for reciprocal movement therein in directions along said axis. The plunger 28 extends from the barrel 11 at the rearward end portion 17 thereof. The plunger 28 has a cross section of cross-shaped configuration (FIG. 3) comprising an elongated stem portion 30 of substantially narrow rectangular cross section and an elongated branch portion 31 of substantially narrow rectangular cross section.

The branch portion 31 of the plunger 28 intersects the stem portion 30 thereof at substantially right angles (FIG. 3) to provide a pair of arms of the same dimensions positioned one on each side of said stem portion in the manner of a cross. The plunger 28 has a forward end 32 (FIG. 2) and a rearward end 33 (FIGS. 2 and 4).

A piston head 34 (FIG. 2) is removably mounted on the forward end 32 of the plunger 28. The piston head 34 is resilient in radial directions from the axis 29 of the plunger 28 and is in frictional engagement with the inside surface of the barrel 11 in a manner whereby fluid in said barrel in the path of said piston head is forced by said piston head in the direction of movement of said piston head.

The stem portion 30 of the plunger 28 is slidably seated in and guided by the notch 19 (FIG. 3) in the rearward portion 17 of the barrel 11 in a manner whereby said plunger is prevented from rotation about its axis 29.

A substantially disclike handle 35 extends from the plunger 28 at the rearward end 33 thereof substantially perpendicularly to the axis 29 of said plunger. The handle 35 may be integrally formed with the plunger 28. The handle 35 is substantially symmetrical with the plunger 28. The handle 35 has a hole 36 (FIG. 4) formed therethrough.

A flexible elongated stringlike member 37 has a maximum length when stretched taut and may comprise string of natural or artificial fiber, wire, plastic, or the like. The flexible member 37 has one end 38 passing through the hole 27 formed through the surface 23 of the flange 22 and secured therein by any suitable means such as, for example, bonding, knotting, crimping, tying, cross pin, or the like. The flexible member 37 has an opposite end 39 passing through the hole 36 formed through the handle 35 and secured therein by any suitable means such as, for example, bonding, knotting, crimping, tying, cross pin, or the like.

As shown in FIG. 2, when the plunger 28 is in any intermediate position in the barrel 11, the flexible member 37 is in nontaut condition and does not affect the position of said plunger relative to said barrel. When the plunger 28 is moved a determined distance in a rearward direction in the barrel 11, however, the flexible member 37 is stretched taut and limits further movement of said plunger in the rearward direction. Since the determined distance is in accordance with the length, from end 38 to end 39, of the flexible member 37, said length may be varied to vary the limit of rearward movement of the plunger 28 thereby correspondingly limiting the volume of fluid charged and discharged by the syringe. The volume of fluid charged and discharged by the syringe of the present invention is constant, due to the limiting of the rearward movement of the plunger 28 by the flexible member 37.

While the invention has been described by means of a specific example and in a specific embodiment, I do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

Claims

What I claim is:

1. A syringe comprising a hollow barrel; a plunger having an axis movably mounted in said barrel for reciprocal movement therein in directions along its axis; and a flexible elongated member having a maximum length when stretched taut and having one end affixed to said barrel and an opposite end affixed to said plunger in a manner whereby when said plunger is moved a determined distance in a predetermined direction said flexible member is stretched taut and limits further movement of said plunger in said predetermined direction, said barrel having an axis, a forward end portion for accommodating a hypodermic needle, a rearward open end portion through which said plunger extends from said barrel and a middle portion between said forward and rearward end portions, said barrel including a notch formed in the rearward end thereof and said plunger including a key protrusion extending parallel to its axis and slidably seated in and guided by said notch in a manner whereby said plunger is prevented from rotation about its axis.

2. A syringe as claimed in claim 1, wherein said flexible member comprises a stringlike member.

3. A syringe as claimed in claim 1, further comprising a handle extending from said plunger at the free end thereof substantially perpendicularly to the axis of said plunger.

4. A syringe as claimed in claim 3, wherein said one end of said flexible member is affixed to said flange and said opposite end of said flexible member is affixed to said handle.

5. A syringe comprising a hollow barrel having an axis, a forward end portion for accommodating a hypodermic needle, said forward end portion including a first conical portion terminating in a second truncated hollow conical portion having an axis of symmetry coincident with the axis of said barrel, a rearward open end portion having a protuberance extending toward said axis and a notch formed in said protuberance and a middle portion between said forward and rearward end portions and integral with and communicating with said second conical portion; a flange extending from said barrel at the rearward end portion thereof substantially perpendicularly to the axis of said barrel, said flange having a substantially ovular surface coaxial with but at a slight angle of inclination with a plane perpendicular to the axis of said barrel and a collar extending substantially perpendicularly from said ovular surface at the periphery thereof to provide a rearwardly opening recess with said ovular surface, the ovular surface of said flange having a hole formed therethrough; a plunger having an axis movably mounted in said barrel for reciprocal movement therein in directions along its axis and extending from said barrel at the rearward end portion thereof, said plunger having a cross section of cross-shaped configuration comprising an elongated stem portion of substantially narrow rectangular cross section and an elongated branch portion of substantially narrow rectangular cross section intersecting said stem portion at substantially right angles to provide a pair of arms of the same dimensions positioned one on each side of said stem portion in the manner of a cross, said plunger having a forward end and a rearward end, a piston head removably mounted on the forward end of said plunger and being resilient in radial directions from the axis of said plunger, said piston head being in frictional engagement with the inside surface of said barrel in a manner whereby fluid in said barrel in the path of said piston head is forced by said piston head in the direction of movement of said piston head, the stem portion of said plunger being slidably seated in and guided by the notch in the rearward portion of said barrel in a manner whereby said plunger is prevented from rotation about its axis; a substantially disclike handle extending from said plunger at the rearward end thereof substantially perpendicularly to the axis of said plunger, said handle being substantially symmetrical with said plunger and having a hole formed therethrough; and a flexible elongated member having a maximum length when stretched taut and having one end passing through the hole formed through the surface of said flange and secured therein and an opposite end passing through the hole formed through said handle and secured therein whereby when said plunger is moved a determined distance in a rearward direction said flexible member is stretched taut and limits further movement of said plunger in said rearward direction.

6. A syringe comprising a hollow barrel, a plunger mounted for reciprocal movement in said barrel along the longitudinal axis thereof, a flexible elongated member having a maximum length when stretched taut and having one end affixed to said barrel and an opposite end affixed to said plunger in a manner whereby when said plunger is moved a determined distance in a predetermined direction said flexible member is stretched taut and limits further movement of said plunger in said predetermined direction, a groove formed in the inner surface of said hollow barrel, a key on an exterior surface of said plunger slidably movable in said groove whereby said plunger is prevented from rotation about its longitudinal axis.