Automatic Retracting Hypodermic Syringe

Abstract

In a hypodermic syringe, automatic retraction, achieved by interposing resilient means between the barrel and the plunger.

Description

My invention relates to a device commonly known in the medical arts by the term "hypodermic" syringe, which is utilized either for the introduction or withdrawal of materials to and from human and animal bodies.

Proper and safe use of such syringes requires first, that air within a syringe be expelled before the attached hollow needle is inserted into a body, and second, that the position of the open end of the needle be ascertained before material is injected.

Sometimes it is desirable that the opening be within a blood vessel or other fluid containing areas. At other times, it is essential that the needle point should not be within such vessels or areas, but rather within other tissues, subcutaneously, or intramuscularly.

Testing for the position of the needle opening merely requires a pulling back, or retraction, of the plunger for a short distance within the barrel of the syringe. This lowers the pressure within the syringe, as well as providing space so that any fluids at the needle tip will flow thru the needle and be seen within the barrel of the syringe. In solid tissues no fluids will be visible.

Retraction should be done every time the position of the needle is changed, whether it is for infiltration of a large area, or merely to prevent a "pooling" when medication is deposited in one area.

In the usual and customary syringes, retraction requires the use of both hands, one to hold the barrel, and the other to pull back on the plunger.

Because two hands are required, many physicians find this procedure awkward and time consuming and therefore it frequently is not performed, exposing a patient to unnecessary discomfort, and danger.

It is known in the art for improvements to facilitate one handed operation of syringes. One such improvement provides a grip for two or more fingers attached to the barrel, with a grip for another finger attached to the plunger.

Another improvement is a complete syringe like barrel and plunger with an opening in said barrel to receive a pre packaged "carpule" of medication, which is then punctured by a special two point ended needle at one end, and griped by a clawlike device attached to the plunger at the other end.

These, and other devices, have the disadvantage of being heavy and difficult to manipulate. They also require sterilization after each use. Further, prepackaging limits choice of medications, as well as leading to waste of unused medication. Finally, they cannot be used with the new, safe, and inexpensive disposable syringes.

A type of retractive aid that can be used with disposable syringes teaches the attachment of a slide piece attached to the plunger, and overriding the barrel. This slide piece is manipulated by the thumb. This proves to be difficult to handle, especially on a small syringe in the order of one to three cc., where the finger pushing the slide runs into the fingers holding the barrel. In a large syringe is is difficult to manipulate when the syringe is three quarters or more full as the slide is pulled up to the end of the syringe with the plunger. Further, a new technique using the thumb axially must be evolved. Also, the slide becomes slippery to manipulate when wet with body fluids.

It is therefore an object of this invention to provide a hypodermic syringe which generally is of standard construction and use, and in which retraction of the plunger can be achieved with the use of only one hand.

Another object of the invention is to provide a hypodermic syringe, the plunger of which automatically retracts when pressure on the plunger is released.

Another object of the invention is to provide a hypodermic syringe that will automatically retract with equal ease at any position of the plunger within the barrel.

Another object of the invention is to provide a syringe which can quickly and easily be adjusted to engage or disengage the automatic retraction improvement.

Another object of the invention is to provide a syringe that facilitates retraction, yet is light and easy to handle in the conventional manner of applying pressure on the plunger.

Another object of the invention is to provide means of automatic retraction simply and inexpensively enough to be used with disposable syringes.

Another object of the invention is to provide means for one handed automatic retraction that can be simply added to the conventional hypodermic syringe.

Other objects and advantages together with the foregoing will be apparent from a consideration of the following specifications and drawings which disclose two embodiments constructed with the principles of the present invention and in which:

FIG. 1 is a perspective view showing one embodiment of the invention in place on a hypodermic syringe.

FIG. 2 is an enlarged perspective view of one embodiment of the invention and the area of attachment to a hypodermic syringe.

FIG. 3 is a fragmentary cross section of one embodiment of the invention, illustrating the extremes of motion of the invention.

FIG. 4 is a cross section, the plane of which is indicated by the line 4--4 in FIG. 3.

FIG. 5 is an exploded fragmentary perspective view showing a second embodiment of the invention and a portion of the syringe plunger.

FIG. 6 is an enlarged cross section view of the second embodiment of the invention in a closed position.

FIG. 7 is a cross section view of the second embodiment of the invention in an open position.

FIG. 8 is a cross section of the second embodiment, the plane of which is indicated by the line 8--8.

In these embodiments, the syringe includes a generally circular cylindrical barrel 10 made of any suitable material such as glass or plastic, and which may be completely or semi transparent.

One end of the barrel 10 is provided with a connector 12 to receive a standard hypodermic needle 14 in the usual way, while the other end of the barrel 10 is provided with an outstanding terminal flange 16 shaped so that it can act as a grip for fingers of the users hand.

The barrel 10 is arranged to receive the plunger 18 which reciprocates therein along the barrel's axis.

In one embodiment the plunger is a usual composite structure and preferably includes a piston 20 which piston has a pair of sealing rims 22 and 24 which make a movable liquid tight fit with the inner aspect of the barrel. The piston 20 is joined to the plunger 18 by means of a through bore (not shown) in the piston heading 22, which bore is forced over a projection (not shown) of the plunger head 25.

The body of the plunger 18 is made up of radially arranged plates 26, 28, 30, and 32 which terminate in the heading 25 at one end, and in a transverse disk heading 34 at the other end.

In accordance with the invention there is provided a shaped resilient piece 36 to move the plunger 18 axially in an outward direction for a short distance within the barrel 10. Said piece is composed of a body 70, and two opposing shaped arms 38 and 40 that arise from it. Said arms have distal edges 42 and 44 which have sharp edges and contact with tension, edges of two of the radially arranged plates of the plunger 18. The contacting distal edges 42 and 44 are centrally concave generally, with peripheral areas also generally concave to facilitate easy engagement and maintenance of the engagement of the edges 42 and 44 with plates of the plunger 18, as well their disengagement.

Altho the piece 36 and any of its essential parts may be integrally part of the barrel 10 or of its flange 16, in this embodiment it is attached by means of its grooved shaped body 70 which permits that it be forced on to the flange 16 where it is maintained in position by friction.

The piece 36 and its component parts are of a resilient material which may plastic, metal, or wire.

Preferably, the edges of the radial plates 26,28,30 and 32 are roughened for better engagement with the arms 38,40.

In use, the syringe would, preferably, be dispensed with the arms 38 and 40 disengaged from any of the radial plates of the plunger 18. Upon filling of the syringe and expelling of the trapped air, injection is made, after which the plunger is turned to bring any two of the radial plates 26,28,30,32 into engagement with the ends of the arms 38 and 40. An initial manual retraction of the plunger 18 in conjunction with the turning of the plunger, will bring the arms to positions 38A and 40A and the attached piston head to 20 A as illustrated in FIG. 3. Then, inward pressure on the plunger 18 to expell material from the syringe will concumatly depress the arms to positions illustrated as 38 B and 40 B, and the piston head to 20B. In this position, because of the angle of the arms, tension is increased so that upon cessation of the expelling pressure, the resilient tension will move the plunger 18 axially within the barrel in an outward direction, thus creating the necessary lessened pressure, as well as space within the barrel 10, as the piston head is moved to position 20 A.

When the plunger is pressed in an inward direction sufficiently to cause the arms 38 and 40 to reach the extent of their range of motion, or the flange 16, the resiliency of the arms will cause them to give way to allow any further inward movement of the plunger. The clicking of this movement caused by the action of the edges of the arms 38 and 40 on the roughened edges of the radial plates of the plunger will give an audial indication of the amounts of fluids expelled into the body.

In the second embodiment, the means for providing automatic retraction include a hypodermic syringe with customary rigid barrel 10, and plunger 18 reciprocal therein, said plunger having attached an improved piston head 46.

The plunger 18 is a composite structure, including radially arranged plates 26 to 32 which terminate in circular headings 25 and 34 at opposing ends. Arising from the inner heading 25 is a circular projection 42. Disposed substantially adjacent and spaced downwardly, is a circular collar 44 for attachment of the piston head 46. Disposed adjacently, and spaced downwardly are two opposing lugs 48 and 50.

The piston head 46, of a customary resilient material that can be either rubber or plastic, is a composite structure with varying degrees of firmness and resiliency achieved by varying the thickness of each of the component parts. Said component parts include the headings 52 and 54, and the connecting circular bellows 56, which is the thinnest component.

The bellows 56 are preferably fabricated in its extended position as shown in FIG. 7 so there will always be a tension within it to cause it to constantly seek this extended position. Other means, not illustrated, but known in the art, may be incorporated to augment this tension.

The piston heading 52 has a through bore 58 which is forced over projection 42 and its circular collar 44 to achieve a liquid proof attachment with the plunger 18.

The piston heading 54 has a through bore 60 which is aligned with the projection 42. Centrally disposed and opening into the bore 60 are two opposing notches 66 and 68 for reception of lugs 48 and 50. Disposed adjacently and spaced upwardly, the bore 60 is elongated at right angles to the notches 66 and 68 to form a slot 62, 64 which easily permits the entrance of the projection 42 and its lugs 48 and 50 into the bore 60 without interference or interlocking. In this position, turning of the plunger 18 will turn the lugs 48 and 50 into the notches 66 and 68 and thus effectively interlock the headings 52 and 54 with the projection 42 which unites the plunger 18 and the piston 46 so that they then function as one piece.

Preferably the syringe will be dispensed with the plunger interlocked as illustrated in FIG. 6, to facilitate withdrawing of material into the syringe, expelling of the air, and injection of the needle into the body.

After injection, the plunger 18 is turned to bring the lugs 48 and 50 into alignment with the slot 62,64. In this unlocked position, cessation of pressure on the plunger will release the tension of the bellows 56 and allow it to extend pulling the projection 42 out of the bore 60 and permitting any liquid at the needle end to flow back into the syringe as illustrated in FIG. 7. To further expel material into the body, pressure is resumed on the plunger 18. As long as there is no turning of the plunger, it will be free to retract at any time pressure on it is relieved .

Claims

As various changes might be made in the embodiments of the invention herein disclosed, as well as other constructions fabricated, without departing from the spirit and principles of the invention, it is understood that all matter herein shown or described shall be deemed illustrative, and not limiting except as set forth in the appended claims, where what I claim as new and desire to protect by Letters Patent is:

1. In a hypodermic syringe comprising a generally cylindrical barrel and a plunger reciprocable in said barrel, the improvement comprising: resilient means incorporated between said barrel and said plunger to provide and transmit a force to move said plunger axially in an outward direction for a limited distance; said resilient means including a piston head of hollow configuration, and capable of distortion in response to movement of said plunger in an inward direction relative to an inner end of said barrel to decrease the effective volume thereof, said piston head returning to relatively unstressed condition upon the release of pressure upon said plunger.

2. Structure in accordance with claim 1, including means for attaching the plunger to the piston head; said means including a projection from the inner heading of the plunger, which projection gives rise to a circular collar, and, adjacently and displaced downwardly, also gives rise to two opposing lugs, and where the piston head is of a composite structure with components of varying resiliency and thickness, including two headings with through bores, the bore of the outer heading allowing its being forced over the collar of the projection to make a liquid tight connection with the plunger, the other heading having around its periphery sealing rims for yielding liquid tight contact with the inner aspect of the barrel, and same other heading having at its outer aspect a partial slot extension of its bore, and immediately adjacent and displaced downwardly and opening centrally into the bore, two opposing notches, said notches receiving, when pressure upon the plunger causes the projection to enter the bore, and upon subsequent turning of the plunger, the lugs of the projection, to interlock both headings of the piston head with the plungers; said headings being connected by a circular bellows attached to the peripheral areas of said headings.

3. A hypodermic syringe as defined in claim 2, wherein said piston head is of a composite construction, with said components being of different thicknesses of resilient material to vary the firmness and resiliency of said components, and wherein the two opposing headings are of a greater thickness than the connecting circular bellows, and wherein said bellows is fabricated with such that resilient force tends to maintain the opposing heads apart from each other in relatively unstressed condition.