JPH05253295A - Discharge injector with precision - Google Patents

Abstract

PURPOSE: To provide a disposable injector which gives a constant injection rate and reduced manufacturing cost. CONSTITUTION: This injector 10 includes a tubular housing 12 which has a rigid cylindrical shell member 14 forming a tubular chamber 17, where the chamber 17 contains a plunger 29 separating it into an air chamber 31 and a liquid chamber 33, and liquid is injected into a patient through a tube 39. The plunger 29 is pushed by an energization means (a spring and so on) to give a constant injection rate.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the controlled release of fluids, and in particular to the precise release of beneficial liquids in syringe type infusion devices.

[0002]

BACKGROUND OF THE INVENTION Devices for injecting into a patient a beneficial agent, such as a drug dispersed in a medical fluid, are known. The most common devices use elevated glass or flexible containers with the beneficial agent diffused into the medical fluid, which is gravitated to the patient's venous system via flexible plastic tubing and catheters. Supplied. The flow rate of this assembly is usually regulated by an adjustable clamp on the tube. This assembly has the drawback of requiring a relatively stationary patient, and relies on the height difference between the source and the patient for precise delivery.

Another type of such device uses electrical / mechanical components in a pump to provide fluid propulsion of a liquid for infusion into a patient. However, such electrically controlled devices have several drawbacks, including not only the cost of such electrical components, but also the limitations that such electrical components and the required power supply impose on the dimensions and portability of the device. Suffer disadvantages.

In the prior art, devices have been used which employ an elastomeric bladder which contains the liquid to be injected under pressure for injection. A typical elastomeric bladder device includes a housing, a bung secured to one end of the housing and including an opening therethrough, and a tubular elastomeric bladder for containing liquid under pressure within the housing. There is. One end of the bladder is sealingly attached to the bung and the inside of the bladder communicates with the opening of the bung. A conduit connected to the bung opening forms a distribution passage with the bung opening for transporting liquid from the bladder to the injection site of the patient. A flow regulator is located somewhere in the dispensing passage to allow liquid to flow from the bladder to the dispensing passage at a predetermined flow rate to the patient.

Another type of infusion device utilizes a syringe-type structure having a piston rod or plunger disposed within the syringe barrel and forming a sliding sealed contact with its inner surface. Biasing means such as springs or elastomeric elements are also provided between the plunger and the front or rear segment of the housing. The liquid to be injected is contained under pressure in the barrel and in the chamber formed by the plunger. The pressurized liquid pushes the plunger against the biasing member, biasing the biasing member to provide a source of liquid under pressure. Pressurized liquid is provided to the patient through conduit means similar to an elastomeric sac type device. These syringe-type infusion devices are generally more cost effective than elastomeric pouch-type devices.

One of the particular problems with prior art injection devices is the achievement of relatively constant flow rates due to liquid injection. This relatively constant flow rate is especially important when long-term infusions such as 24 or 48 hours are required for drug therapy. In infusion devices that use elastomeric bladder, such relatively constant flow rates have been achieved by such means as prestressing the elastomeric bladder and the use of expensive bladder material. The use of such additional prestressed housing or expensive bladder material, of course, adds to the cost of such disposable injectors.

What would be desirable, therefore, would be a disposable injector that is capable of providing a relatively constant flow rate even over long injection periods while maintaining relatively low fabrication and material cost factors. The present invention fulfills these needs.

[0008]

SUMMARY OF THE INVENTION The present invention provides a syringe-type disposable infusion device having biasing means for driving a plunger to generate a source of pressurized liquid in a syringe barrel.
The invention further provides means for providing a relatively constant flow rate of infusion, in addition to the biasing means. These means may further include means for reducing the friction applied to the plunger as the liquid is injected, or for restricting the inflow of air as the liquid is injected.

In the preferred embodiment, the means for providing a relatively constant flow rate provides a barrel having an inner diameter that is tapered in relation to the reduction of the biasing pressure exerted on the liquid to be injected. Including that. The use of such a taper results in a normal force reduction and a corresponding reduction in the friction exerted by the barrel on the plunger such that the amount of biasing pressure exerted on the liquid to be injected decreases over the injection time. Let In another preferred embodiment, the inner diameter of the barrel can be stepped at a number of different diameters that can be controlled to achieve the desired flow curve.

In yet another embodiment for providing a relatively constant flow rate, a plunger having a plurality of flexible sealing elements that form a seal between the plunger and the interior surface of the syringe barrel is used. .. In another embodiment, the flexible sealing element is a biased O-ring held within a groove formed on the plunger. By using multiple seals on the inner surface of the plunger and barrel, the size, resilience and shape of the seals can be manipulated to obtain the desired flow characteristics.

In yet another embodiment for providing a relatively constant flow rate, means are provided for limiting the partial vacuum created in the space within the barrel that is evacuated when the plunger moves forward. In the preferred embodiment, a series of air restrictors are provided in the barrel to gradually reduce the vacuum pressure in connection with the reduction of the biasing pressure applied to the liquid to provide the desired flow characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a syringe type injection device.

FIG. 2 is a cross-sectional view of the first embodiment of the syringe type injection device.

FIG. 3 is a cross-sectional view of an alternative embodiment of the syringe type injection device.

FIG. 4 is a cross-sectional view of a syringe barrel using a first preferred embodiment of the means for adjusting the infusion rate according to the principles of the present invention.

FIG. 5 is a cross-sectional view of a second preferred embodiment of the means for adjusting the injection flow rate according to the principles of the present invention.

FIG. 6 is a cross-sectional view of a plunger using yet another embodiment of the means for adjusting the injection flow rate in accordance with the principles of the present invention.

FIG. 7 is a cross-sectional view of a syringe barrel using yet another embodiment of the means for adjusting the infusion flow rate in accordance with the principles of the present invention.

[0019]

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS Referring to FIG. 1, a perspective view of a syringe type infusion device, generally designated by the reference numeral 10, is seen. The injector 10 includes a tubular housing 12 having a rigid cylindrical barrel member 14 forming a tubular chamber 17. The rigid cylindrical body 14 is preferably molded of a transparent material such as plastic to allow visual inspection of the interior of the tubular member. A volume graduation 18, which is printed, imprinted or otherwise applied to the barrel wall, is also preferably provided.

At the rear end of the cylindrical body 14, there are two openings 51, 5
A rear end cap 20 having 3 is sealingly connected. A front end cap 22 having two openings 24 and 26 is sealingly connected to the front end of the cylindrical body 14. Cylindrical barrel 14, rear end cap 20 and front end cap together form a tubular chamber 17 of injector 10. Within the tubular chamber 17 is housed a plunger 29 which divides the tubular chamber 17 into an air chamber 31 and a liquid chamber 33 as best seen in FIGS.

There is an outlet port 35 in the first opening 24 provided in the front end cap 22. A discharge conduit 37, including a tube 39, sealingly engages the outlet port 35, such as with an adhesive. Tube 39 includes a root end and a tip. The proximal end of the tube 39 is fixed to the outlet port 35 with an adhesive or the like. Alternatively, the tube 39 is sold unconnected to the housing 12 and may include means for attachment to the outlet port, such as a locking luer connection.

The tip of the tube 39 is sealingly engaged with the rigid housing 42 by an adhesive or the like. The rigid housing 42 preferably includes a luer connector for connection to a catheter to be inserted into the patient's venous system (not shown). The rigid housing is also preferably US Pat. No. 4,7,7 entitled "Injector with Terminal Flow Regulator".
No. 41,733, including a glass capillary flow regulator.

The second opening 26 formed in the front end cap 22 is an inlet port 44. The inlet port 44 is preferably pierceable with a sharp cannula during filling,
And a liquid chamber 33 of the injector 10, such as an elastomeric septum 46 that can be resealed when cannulated.
Includes means to allow regulated access to. Alternatively, a check valve can be provided that allows liquid to enter the fluid chamber 33 through the valve, but prevents liquid from escaping the liquid chamber 33.

Referring now to FIG. 2, a cross sectional view of a syringe type injector is seen. The front end cap 22 is the injector 1
A recess 49 aligned with the inlet port is provided for sealingly containing an elastomeric septum 46 that allows zero access to the liquid chamber 33. The front end cap 22 is also an outlet port 35, as previously discussed, and an inner securement area 36 (FIG. 4) that receives a tube 39 for sealing engagement.
And best seen in 5).

The first opening 51 in the rear end cap 20 allows air to pass from the air chamber 31 to the external environment. Check valve 55 provided on the first opening 51
Prevents backflow of air from the external environment into the air chamber 31. As a result, when liquid under pressure is inserted into the inlet port 44 of the front end cap 22 and the plunger 29 moves rearward, the first opening 51 cooperates with the check valve 55 to allow the air in the air chamber 31 to move. Allow escape from injector 10.

The trailing end cap 20 includes a recess 59 (best seen in FIGS. 4 and 5) aligned with the second opening 53. In the recess 58, an air regulator 60 that regulates the air flow from the external environment to the air chamber 31.
Is stored in a seal. In the preferred embodiment, the air regulator 60 can be a piece of porous material such as is commonly used for filtration. A seal member such as an adhesive tape 61 is provided on the rear end cap 20 to prevent the liquid from being injected before removing the seal member.

As previously mentioned, the air chamber 31
And the liquid chamber 33 is divided into the plunger 2
It is 9. Plunger 29 includes outwardly projecting ribs 62, 64 sized and shaped to establish a slidable sealing engagement with the inner surface 16 of the barrel. The outwardly projecting ribs 62, 64 provide a slidable seal engagement, but to minimize friction between the plunger 29 and the inner surface 16 of the barrel 14, polypropylene coated rubber,
It is preferably made of silicone rubber, coated neoprene or a similar type of material.

Plunger 2 to provide a source of pressurized liquid
It is provided in a biasing means cylinder 14 which works together with 9. Figure 2
In the embodiment shown in FIG. 3, this biasing means is held in compression in the air chamber 31 by the plunger 29 and the rear end cap 20. This biasing means in the preferred embodiment is a spring 66. The spring 66 is the plunger 29.
, Which is under compression along the entire length of the barrel regardless of its position, minimizes variations in the biasing force exerted on the plunger 29 by the spring 66. In the preferred embodiment, the spring 66
Is made of stainless steel.

In the preferred embodiment shown in FIG. 3,
This urging means is provided in the liquid chamber 33 for the plunger 2
9 and the front end cap 22 are held in an inflated state. This biasing means in the preferred embodiment is an elastomeric member 68. Again, this elastomeric member 68 is inflated and held along the entire length of the barrel regardless of the position of the plunger 29, and the elastomeric member 68 causes the plunger 29 to expand.
The fluctuation of the biasing force applied to is minimized.

Despite the use of prestressed biasing members, the force exerted on the plunger by the biasing means generally decreases as the prestressed condition of the biasing members is relieved. This results in the liquid source in the liquid chamber 33 being under greater pressure near the beginning of injection as compared to the liquid pressure near the end of the injection time. This decreasing hydraulic pressure results in a decreasing flow rate over the injection time.

Referring to FIG. 4, there is shown a cross-sectional view of a barrel 14 made in accordance with the principles of the present invention. As previously discussed, the plunger 29 has a pair of outwardly projecting ribs 62, 64 that form a sliding sealing engagement with the inner surface 16 of the barrel 14. In the device shown in FIG. 4, the inside diameter (d) of the barrel is the original inside diameter (d) of the front portion of the barrel.
The taper from i) to the final inner diameter (df) in the rear part of the barrel. The initial inner diameter (di) seen in the forward portion is the final inner diameter (df) seen in the rear portion.
Greater than However, the torso 14 along all parts of the torso
Inner surface 16 is within a diameter range sufficient to cooperate with the outwardly projecting ribs of the plunger to maintain the sliding sealing engagement.

Therefore, the frictional force applied to the plunger 29 in the rear portion of the body 14 is larger than the frictional force applied to the plunger 29 in the front portion of the body 14. As will be appreciated by those skilled in the art, this frictional force can be synchronized with the force applied by the biasing means to achieve a constant flow rate by adjusting the degree of taper of the barrel. It should be noted that the taper shown in FIG. 4 is exaggerated for purposes of illustration and the taper of the actual embodiment is much smaller.

Referring now to FIG. 5, an alternative embodiment of the barrel 14 in accordance with the principles of the present invention can be seen. In this embodiment, the barrel 14 has a constant diameter area (di, d, d
f) includes a plurality of abutment diameters. From the original anterior diameter area (di) to the smaller posterior diameter area (d)
By stepping these zones (di, d, df) up to f), a steady flow rate can almost be achieved.
In addition, for example, if an initial large dose of the drug is needed,
Various combinations of diameter zones can be employed to change the drug flow characteristics. Again, as will be appreciated by those skilled in the art,
The diameters of the zones will be coordinated with the force exerted by the biasing means to achieve the desired flow characteristics. Again, the steps shown in FIG. 5 are exaggerated for purposes of illustration,
The steps in the actual embodiment are smaller.

Referring now to FIG. 6, there is seen a cross section of a plunger 29 made in accordance with the principles of the present invention. In this plunger 29, the integral outwardly projecting member is replaced by a plurality of flexible sealing elements such as rubber O-rings 71. 0-ring 71
Is housed in a groove 73 formed in the plunger 29.

By separating the sliding sealing member in this manner, it is possible to optimize the sliding sealing member independently of the plunger body with respect to member position, material, shape and degree of contact with the barrel. is there.

Referring now to FIG. 7, an alternative embodiment for achieving steady flow is seen. FIG. 7 shows a cross-sectional view of an alternative embodiment of the injector 10 with similar elements designated by the same reference numbers.

In this embodiment, the rear end cap 12
An air restrictor 60 housed therein limits the intake of air and maintains a partial vacuum in the air chamber 31. In addition to the air restrictor 60, there are a plurality of air restrictors 76, 78 within the cylinder 14 at points spaced along the longitudinal axis of the cylinder 14.
80 are accommodated. The plunger 29 includes a plurality of air restrictors 76, when the liquid chamber 33 is filled with liquid.
78 and 80 are inflated by the barrel 14 so that they are sealed off. As the plunger 29 moves forward, it progressively advances through the plurality of air restrictors 76, 78, 80, opening these filters in turn to the outside environment. More air in the air chamber 31
Plunger 2 by gradually allowing access to
A vacuum can be maintained in the air chamber 31 that gradually weakens as the 9 moves forward. This varying force exerted on the plunger 29 offsets the varying force exerted by the biasing member 68 on the plunger 29, thereby allowing a steady flow rate. Again, the degree of vacuum can be tuned to cancel the specific force characteristics of the biasing member, as will be appreciated by those skilled in the art.

It is to be understood that various changes and modifications to the embodiments described herein will be apparent to those of ordinary skill in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its benefits. It is therefore intended that such changes and modifications be covered by the claims.

[Brief description of drawings]

FIG. 1 is a perspective view of a syringe-type injection device.

FIG. 2 is a cross-sectional view of a first specific example of a syringe-type injection device.

FIG. 3 is a cross-sectional view of an alternative embodiment of a syringe-type injection device.

FIG. 4 is a sectional view of the syringe barrel of the first embodiment according to the present invention.

FIG. 5 is a sectional view of the syringe barrel of the second embodiment according to the present invention.

FIG. 6 is a sectional view of a plunger.

FIG. 7 is a cross-sectional view of another embodiment of a syringe barrel according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Injection part type injection device 12 Tubular housing 14 Cylindrical body member 20 Rear end cap 22 Front end cap 29 Plunger 31 Air chamber 33 Liquid chamber

 ─────────────────────────────────────────────────── --Continued Front Page (72) Inventor Steve, Hessel 92708, Fountain Valley, California 92708, USA 9064, USA

Claims (13)

[Claims] 1. A tubular housing forming a tubular chamber having an inner surface, slidably housed within the tubular chamber to form a liquid tight seal with the chamber, and airing the chamber. A plunger that is divided into a chamber and a liquid chamber, the liquid chamber being in fluid communication with a release conduit that may connect to the venous system of the patient; and a source of pressurized liquid within the liquid chamber. For providing a patient with a biasing means provided between the plunger and one end of the tubular housing and a means for providing a relatively constant infusion flow rate independent of the biasing means. Device for injecting liquid into. 2. The apparatus of claim 1 wherein said biasing means is held in compression between the plunger and the end of the air chamber. 3. The apparatus of claim 1 wherein said biasing means is held in an inflated condition between the plunger and the end of the liquid chamber. 4. The apparatus of claim 1 wherein said means for providing a relatively constant flow rate comprises a taper on the inner surface of the tubular housing. 5. The apparatus of claim 4 further including a stepped taper on the inner surface of the tubular housing. 6. A plurality of flexible sealing elements included on the plunger to form a seal between the plunger and the inner surface of the tubular housing, the means for providing a relatively constant flow rate. The apparatus of claim 1 including. 7. The apparatus of claim 6 wherein said flexible sealing element is a biased O-ring retained within a groove formed in the plunger. 8. The apparatus of claim 1 wherein said means for providing a relatively constant flow rate includes means for adjusting the partial vacuum in the air chamber. 9. The apparatus of claim 8 wherein the means for adjusting the partial vacuum comprises an air restrictor provided between the air chamber and the atmosphere. 10. The apparatus of claim 9, wherein the air restrictor is an air filter. 11. The means for adjusting the partial vacuum comprises:
9. The device of claim 8 which is an array of air restrictors provided in the tubular housing between the air chamber and the atmosphere. 12. The apparatus of claim 1 wherein said means for providing a relatively constant flow rate includes means for reducing friction applied to the plunger as the liquid is injected. 13. The apparatus of claim 1 wherein said means for providing a relatively constant flow rate includes means for controlling the inflow of air as the fluid is injected.