HK1061816B - Adjustable dosage syringe - Google Patents

Description

Dosage-adjustable syringe

Technical Field

The present invention relates to an adjustable dose syringe and more particularly to an auto-zeroing syringe which can be loaded at one time to give multiple doses.

Background

Adjustable dose syringes are already known in the art, i.e. syringes that can be used to adjust a specific given dose of the syringe contents and/or to perform multiple doses given by multiple separate injections of the adjusted syringe contents. For example, in veterinary applications, the specific dosage of the agent to livestock will vary widely depending on the weight of the livestock. Therefore, when a herd of livestock needs to be injected with a drug, accurate charging of the injector in the field is often not possible. Thus, syringes typically provided to veterinarians can be adjusted to deliver a dose. Such syringes are typically single use syringes and thus, the veterinarian can select the appropriate dose for each animal, set the syringe immediately at the given dose, inject the animal, and then discard the syringe with the remaining liquid. Alternatively, when a large number of animals are to be administered, multiple doses for a number of animals may be contained in a single syringe. The veterinarian selects the appropriate dose for each animal, immediately sets the dose on the syringe and sequentially injects those animals with the appropriate dose.

Since large volumes of livestock are often handled in a short period of time, it is important that such adjustable syringes be capable of rapid adjustment of the precisely administered dose. Furthermore, since such syringes are typically disposable, the structure must be inexpensive to manufacture. In addition, the manufacturer typically supplies the syringe and drug in a kit. Thus, the adjustable syringe must be able to deliver different doses according to the weight of the animal and the dose increment to which the syringe can be set should be relatively small.

U.S. patent 4,275,729 describes an adjustable dose syringe in which the syringe plunger has a plurality of saw-notch like indentations spaced closely along its length, and a dose selection ring surrounding the plunger. Two projections are provided on the inner periphery of the dose selection ring, which are aligned and enter one of the notches of the first set of notches, and when one projection enters one of the notches of the first set of notches, the other projection also enters the second set of notches. In accordance with the invention, the desired shot size of the syringe contents is discharged when the plunger engages the plunger receiving end of the syringe barrel at the other end of the syringe barrel.

The above patents also describe some prior art patented syringes. U.S. patent No.3,563,240 proposes a syringe having a plunger with a circumferential thread and a nut engaging the circumferential thread. The nut is threaded onto and off the syringe plunger, and the nut blocks the plunger from further depression within the syringe barrel, thereby providing an adjustable dosage of the drug in the syringe. However, manually screwing the nut down the plunger takes time, especially when the dosage requirements vary greatly between animals, and in order to ensure that the correct dosage is given, screwing of the nut must be done accurately. Such syringes are also expensive to manufacture because of the manual operation required to screw the nut onto the plunger during assembly.

Efforts have been made in the prior art to overcome these disadvantages and it is worth noting a syringe of the so-called "split ring" type in which a "screw cap" is releasably hinged about the circumference of the syringe. Thus, the nut can be opened, manually slid onto the plunger to obtain the desired dosage, and then closed onto the threads to expel the appropriate dosage from the syringe. However, this still requires manual opening and closing of the hinged "nut," which takes a lot of time for the reasons mentioned above.

Some older prior art methods have addressed some of the problems discussed above by providing the plunger with various forms of movable stop mechanisms, such as pins, clips and the like, but these methods are inconvenient to use in the field. In the older art, there is a method of providing a gap in a ring around the plunger through which the ring can be raised and moved along the plunger to an interrupted groove in the side of the plunger. This ring can be lowered and set the dose expelled by the plunger. Us patent 2,856,925 is representative of this approach. This older method, while relatively fast to operate, has the disadvantage that the dosage is determined by the size of the plunger side recess. Thus, the recess has clearance to allow the ring to enter, which makes it impossible to accurately set the dose expelled by the syringe.

Thus, while advances in the art have improved the accuracy with which doses can be administered, i.e., by nut mechanisms and the like, these advances have also been associated with syringes that are inconvenient to use and difficult to operate quickly. Thus, a significant advance in the art has been the provision of a variable dose syringe which not only allows rapid changes in the setting of a given dose, but also allows very accurate setting of the dose and allows very small increments in the dose adjustment.

Brief description of the drawings

FIG. 1 is an exploded view of the syringe of the present invention showing a preferred embodiment of the invention, the center line indicating how the parts are assembled;

FIG. 2 shows a ring assembly on a plunger and a syringe tube assembly with a seal inserted within the tube;

FIG. 3 is a front elevational view of the syringe with the plunger engaged with the seal and the dose selection ring in a fully depressed position, indicating that a selected dose has been administered;

FIG. 4 is a front view similar to FIG. 3 showing the plunger engaged with the seal and the dose selection ring rotated in a counterclockwise direction to a selected dose setting position;

FIG. 5 is a front view similar to FIG. 3, showing the plunger in a fully depressed position expelling a selected dose;

fig. 6 is a front view similar to fig. 3 showing the plunger engaged with the seal and the dose selection ring in a selected dose setting position.

FIG. 7 is a front view similar to FIG. 6, showing the plunger in a fully depressed position expelling a selected dose;

FIG. 8 is a front elevation view of the syringe showing the syringe barrel in cross-section with the syringe barrel in pressing contact with the seal and with a small gap between the syringe barrel and the plunger;

FIG. 9 is a top view of the dose selection ring;

FIG. 10 is a side view of the dose selection ring showing the scale on the sleeve;

FIG. 11 is a cross-sectional view of the dose selection ring showing threads on the ring;

FIG. 12 is a linear development of FIG. 11;

FIG. 13 is an outside elevational view of the seal;

FIG. 14 is a cross-sectional view of the seal;

FIG. 15 is a bottom view of the seal;

fig. 16 is a top view of the seal.

Disclosure of Invention

The present invention comprises an auto-zero dose syringe comprising a syringe barrel, a plunger and a dose selection ring. The syringe barrel has an internal length and diameter that forms a volume sufficient to contain multiple doses of a medical fluid. The syringe barrel is provided with a discharge end at one end and a plunger receiving end at the other end. In order to keep the contents of the syringe from leaking and to withstand the pressure exerted by the discharge of the contents, a seal is arranged over the contents. The seal is shaped to engage a mechanism for generating pressure to expel the contents of the syringe. The plunger acts as a mechanism for generating pressure to expel the contents of the syringe. A plunger is movably disposed within the syringe barrel, the plunger having a length greater than the length of the syringe barrel, the plunger further having a plurality of closely spaced indentations along the length. The end of the plunger within the barrel (distal end) is shaped to allow the plunger to exert pressure on the contents of the syringe to expel them. The plunger tip is preferably shaped to engage with a corresponding portion of the seal formed by the seal in direct contact with the contents of the syringe barrel.

A dose selection ring is movably and rotatably disposed about the plunger. The ring is at least partially disposed on the inner circumference of the syringe barrel. The syringe is characterised in that the dose selection ring is provided with a sleeve which is movably located within the syringe barrel, the sleeve being provided with a scale, the desired dose being settable by rotating the selection ring to the desired dose scale. In this embodiment of the invention, when the selection ring is rotated counter-clockwise to set the desired dose, the threads on the inner circumferential surface of the ring enter the notches in the plunger, thereby forming a positive lock therebetween. The interengagement of the ring and the plunger enables the ring and the plunger to move together. When the ring is moved to its stop surface (flange) against the syringe barrel (flange), the ring and plunger are prevented from advancing. It will be appreciated that this is the point at which the desired dose is expelled. Thus, with each dose expelled, the injector is set to zero, and thus the injector may be defined as auto-zero. The distance traveled by the plunger relative to the inside diameter of the syringe determines the amount of contents expelled from the syringe. When not in use, the discharge end of the syringe may be closed by a removable stopper or cap.

The present invention is superior to prior art injectors which are less accurate because the zero point is predetermined and not fixed. Thus, there is some degree of inaccuracy due to variable filling volumes. The change in fill volume affects the volume of product expelled from the syringe, thereby resulting in over-dosing or under-dosing. The difference in fill volume occurs when the plunger is moved to expel the air from the syringe contents.

The invention also has the advantage that the scale on the dose selection collar barrel is spaced less apart, and closely spaced scales allow for more accurate dosing than widely spaced scales.

Detailed Description

The invention may be further understood with reference to the following drawings. Figure 1 shows an exploded view of a preferred embodiment of the present invention. The syringe is shown comprised of a syringe barrel 10 having an interior length L and an interior diameter D. The volume formed by dimensions L and D is sufficient to contain multiple doses of a liquid, such as a drug, in the syringe. The syringe barrel has a discharge end 11 which in this embodiment of the invention is tapered on the extended end of the syringe barrel and at the other end of the length of the syringe barrel is a plunger receiving end 12. In this embodiment of the invention, the plunger receiving end 12 of the syringe barrel is formed as a flange-type receiving end.

Plunger 50, shown in fig. 1, is typically longer than the length of the syringe barrel. The plunger has a mechanism for engaging the dose selection ring including a notched portion disposed along the length of the plunger. Preferably, the plunger has at least two sets of notched portions as indicated at 53 in figure 1. The specific shape of the notch is not critical. The cross-sectional shape of the notch may be square, rectangular, oval, etc., but it is only necessary that the raised portion on the selector ring have the same shape so that the notch and raised portion achieve the desired engagement. Preferably the notches are inclined inwardly so that the threads on the ring can smoothly move along the plunger. The distal end of the plunger (within the syringe barrel) is shaped to attach to the seal and apply sufficient pressure to the seal to push the seal to expel the contents of the syringe barrel. To connect to the seal, the plunger is configured to contact the seal in any convenient manner that will connect and/or create pressure when the plunger is depressed. In this embodiment of the invention, the plunger tip, preferably the tip, is machined or otherwise fitted with a first plate 54, as shown in FIG. 1. Thus, the plunger need only generate sufficient pull-back force to dislodge from the seal. Above the first plate is arranged a second plate 56, as shown in fig. 1, having a larger diameter than the first plate, which acts to create a pressure on the seal. The exposed end of the plunger is provided with a female backing plate 58.

The sealing mechanism (seal) is arranged to cover the contents of the syringe barrel all the way, which prevents leakage of the contents and/or can withstand the pressure exerted to push the seal to expel the contents. In this embodiment of the invention, the seal 30 is shown in FIG. 13 in frictional contact with the inner circumference of the syringe barrel. To assist in creating the frictional contact, the sealing wall (i.e., upper portion) extending above the conical section 31 of FIG. 13 is flanged, thereby creating a gap 39 as shown in FIG. 14. The seal has a hollow structure that receives the plunger and bears the pressure generated by the plunger to expel the contents of the syringe barrel. To accommodate the plunger, the seal has a first tubular housing which extends upwardly from the inner wall of the cone 31 of the seal as shown in figure 13. The first tubular housing 38 shown in fig. 14 is preferably formed as a snap-fit assembly wherein the housing wall 37 is interrupted and can be deformed to receive the plunger and be secured closed. In this embodiment of the invention, the first housing releasably receives the plunger neck 57 shown in fig. 1. The seal also has a second tubular housing 36, shown in figure 14, which is larger in diameter than the first housing. The second tubular housing also extends upwardly from the inner wall of the cone 31 shown in figure 13. The face of the second housing abuts a plate 56 into which the plunger is inserted, thereby being able to withstand the pressure exerted by the plunger. Preferably, a projection 33 is provided on the face to limit rotation of the plunger within the housing. In this embodiment of the invention, two bumps are arranged on the housing face. The plunger is restricted from rotating when its side abuts the tab. To assist in receiving the plunger into the seal, the upper portion of the seal is formed in the shape of a ridge along the periphery. The ridge extends sufficiently to contact the side of the plunger when the plunger is inserted into the seal, thereby guiding the plunger into the seal housing. The ridge portion of the seal is shown in cross-section in fig. 14, and is represented by parallel straight lines across the upper portion of the seal. This ridge portion is further shown in the top view of fig. 16, and is represented by a concentric circle between a circle representing the outermost periphery of the housing and the inner periphery of the upper portion of the seal. A unique feature of the present invention is that the plunger can be removed from one syringe and reused with another syringe barrel already containing the contents enclosed by the seal described herein.

As can be seen in fig. 2, the dose selection ring 41 has a sleeve 42 which can be placed around the plunger (notched portion) with a portion inside the syringe barrel. The outer circumference of the ring is preferably closely spaced from the inner circumference of the syringe barrel. The sleeve is marked with a scale 43 for setting the desired dose. The dose selection ring also has a mechanism to engage the plunger. The ring engagement mechanism includes a raised portion disposed along the inner circumferential surface of the ring, the raised portion being shaped for aligned engagement with the plunger. For example, the raised portion may enter the notch 53 on the plunger 50 shown in fig. 1. In this embodiment of the invention the raised portion is a thread along the inner circumferential surface of the ring and has two offset open ends 45 and 46 which allow the thread to engage the indentations of the plunger. The two raised portions are arranged such that when one of the two raised portions enters the first set of indentations, the other raised portion enters the other set of indentations. The tab portion can be aligned with the notch portion by rotating the ring about the plunger axis. The specific shape of the convex portion is not strictly defined. The cross-sectional shape of the protruding portion may be square, oval, etc., but it is necessary that the indentations have the same shape so that the indentations can achieve the desired engagement with the protruding portion.

It is also a unique feature of the present invention to mark the outside of the dose selection ring with a scale. Due to this feature, and due to the fact that the diameter of the dose selecting ring is only slightly smaller than the inner diameter of the syringe barrel, the dose can be accurately dispensed. By rotating the dose selection ring in a counter-clockwise direction, the ring slides longitudinally along the length of the plunger indicating the desired dose.

The dose can be selected visually by aligning the scale with the rim of the syringe barrel. Preferably, a line of sight is formed from which the ring is set to select a dose. If the line is not perfectly vertical, the dose will not be accurate. These arrangements of the present invention are very compact and therefore have a very low probability of error. In contrast, conventional syringes have a long distance between the scale and the syringe barrel. Even more disadvantageously, in conventional syringes the scale is at the level of the plunger. Once the scale is set at the desired dose, the ring remains in forced locking engagement with the plunger.

Although a seal is provided between the sleeve and the syringe barrel, a syringe without a seal may be used because the outer diameter of the sleeve is only slightly larger than the inner diameter of the syringe barrel. To expel the contents of the syringe barrel, the ring and/or plunger are slid until the ring contacts the syringe barrel. In this way, the desired dose of substance is expelled from the discharge end of the syringe barrel. The amount of material expelled by the syringe is determined by the distance the plunger moves relative to the diameter of the syringe. Thus, the capacity is equal to the travel distance multiplied by the cross-sectional area.

Any suitable material or method may be used in the syringe manufacturing process. Preferably, the plastic can be molded into various parts of the syringe. Alternatively, other materials such as glass, metals, and combinations thereof may be used if desired. The syringe can be manufactured at low cost by such a method of manufacturing the respective parts of the syringe. The syringe may be assembled by simply sliding the dose selection ring over the plunger from the opposite end of the concave backing plate and then inserting the plunger into the syringe barrel with the contents already contained. Alternatively, the female backing plate may be removable by methods known in the art to facilitate sliding the dose selection ring 40 over the plunger.

Generally, syringes of this construction are configured to accommodate the amount of material that needs to be dispensed. Typically, the total volume of the various syringes is as small as 3 cubic centimeters and as large as 300 cubic centimeters, but volumes between 20 and 150 cubic centimeters are more common. Multi-dose syringes of around 30 cubic centimeters are considered particularly useful because such volumetric syringes can be used to administer drugs to many animals, with 1 to 5 cubic centimeters per dose being common.

The syringe may be filled by any suitable method, preferably by a conventional automatic filling machine. Typically, the syringe barrel is filled directly from the plunger receiving end. After the desired amount of material has been filled, a seal is placed against the top end of the refill near the receiving end of the plunger. The seal is placed so that there is a sealed and movable contact between the outer circumference of the seal and the inner circumference of the syringe barrel. Another method of filling the syringe is to place a cartridge or bag within the plunger, which contains the material to be expelled from the syringe barrel. Due to the different filling methods, the syringe barrel and the contents of the plunger should have corresponding sealing means to effectively apply pressure to expel the material.

Such syringes are well suited for dispensing substances in predetermined amounts. For example, such a syringe may be used to administer a substance to livestock by placing the port at the end of the syringe in a position to administer the substance to the livestock mouth and then pressing the concave backing plate until the dose selection ring contacts the syringe barrel. Such a syringe is particularly suitable for dispensing pasty substances.

Another unique feature of the present invention is the ability to withdraw the plunger from one syringe barrel along with the dose selection ring and use it with another syringe barrel along with the dose selection ring.

While the invention has been described with reference to certain preferred embodiments thereof, it will be apparent to those skilled in the art that modifications may be made to the invention, and it is intended that the invention encompass such obvious modifications. Accordingly, the invention extends to the spirit and scope as set forth in the appended claims.

Claims (6)

1. An auto-zero dose injector comprising:

(a) a syringe barrel having an interior length and diameter defining a volume sufficient to contain a desired amount of liquid, a discharge end at one end of said syringe barrel, a plunger receiving end at the other end of said syringe barrel,

(b) a plunger movably disposed within the syringe barrel and having a length greater than a length of the syringe barrel, the plunger having a plurality of closely spaced indentations disposed along the length, an

(c) A movable dose selection ring surrounding the plunger and rotatable about the plunger longitudinal axis; characterised in that the dose selection ring has

(1) A sleeve within the syringe barrel;

(2) the sleeve of the dose selection ring is marked with scales, and the required dose can be set by rotating the dose selection ring until the scales of the required dose are reached;

(3) a mechanism for engaging the dose selection ring with the plunger may move the ring and plunger together until the stop surface of the ring abuts the syringe barrel, thereby releasing the desired dose.

2. The syringe of claim 1, wherein the ring is moved by a raised portion disposed along the plunger.

3. The syringe of claim 2, wherein a threaded displacement mechanism is disposed on an inner circumferential surface of the ring.

4. The syringe of claim 1 wherein the ring is rotated counterclockwise to the desired dose scale.

5. The syringe of claim 1 wherein the mechanism for engaging the ring with the plunger is a locking mechanism consisting of threads on the ring and a notched portion on the plunger.

6. The syringe of claim 1 wherein the dose selection ring is automatically zeroed when it contacts the syringe barrel.