Patent Application
20080167618
The present invention relates to an infusion pump assembly for controlled delivery of a pharmaceutical product to a subject, and more specifically to a syringe assembly for use with the infusion pump.
Infusion pumps provide a significant lifestyle benefit for individuals requiring multiple deliveries of volumetrically proportioned medication to their body over a period of time. Infusion pumps reliably dispense the required medication to the patient through an infusion path established between the patient and the pump. The infusion path is a conduit secured to the pump system at one end and secured intravenously or subcutaneously to a patient on the other. The operation of the infusion pump is controlled by a processor. The processor controls the delivery of periodic dosages of medication to a patient at predetermined times. Thus, a patient is able to rely on the infusion pump for delivering the required dosage of medication intravenously or subcutaneously over a period of time. In this way, the patient need not interrupt life activities for repeated manual delivery of required medication.
As is known, infusion pumps often employ a piston-type drive mechanism for urging the contents of a pharmaceutical cartridge or “syringe assembly” internal to the pump along the infusion path to the subject. The piston-type drive selectively drives the syringe plunger to dispense a desired amount of fluid from the syringe housing.
The features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by the apparatus, and the method of practicing the invention, particularly pointed out in the written description and claims below, as well as in the attached drawings.
In accordance with an aspect of the invention, a syringe assembly for use with an infusion pump having a drive piston is provided. The syringe assembly comprises a substantially hollow syringe housing and a plunger axially movable within the syringe housing to dispense a fluid therefrom. The plunger has a body with a portion thereof configured to engage a radially elastic member associated with the drive piston such that the plunger is releasably axially secured relative to the drive piston.
In accordance with another aspect of the invention, an infusion pump assembly is provided. The infusion pump assembly comprises an insulin pump including a drive piston having a radially elastic member associated therewith, and a syringe assembly. The syringe assembly includes a substantially hollow syringe housing and a plunger axially movable within the syringe housing to dispense a fluid therefrom, the plunger having a body with a portion configured to engage the radially elastic member associated with the drive piston such that the plunger is releasably axially secured relative to the drive piston.
In accordance with another aspect of the invention, the drive piston has a first annular groove and the plunger has a second annular groove. The radially elastic member is positional within the first and second grooves to releasably, axially secure the plunger relative to the drive piston.
The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown various embodiments. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
In the drawings:
Certain terminology is used in the following description for convenience only and is not limiting. The words “right,” “left,” “lower” and “upper” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the infusion pump and designated parts thereof. The terminology includes the words specifically mentioned above, derivatives thereof and words of similar import.
Referring to
In operation, processing circuitry 200, powered by power cells 70, controls the operation of infusion pump 5. Motor 10 is incrementally engaged to infuse medication to a patient at predetermined intervals. Upon engagement, motor 10 causes lead screw 15 to rotate by means of gear train 28. When lead screw 15 is driven by motor 10, drive piston 22 is driven axially toward syringe assembly 12, thereby pushing plunger 20. This causes delivery of medication 24 from within syringe housing 26 of syringe assembly 12. Infusion path 14 is connected by connector 27 to dispensing tip 25 (see
Referring now to
The present invention is not limited to the illustrated infusion pump. Infusion pump 5 may have various configurations including various controls, power sources, drive means, access ports and doors, sizes and shapes.
Referring to
In the present embodiment, plunger 20 includes tubular body 31 which has a generally hollow interior 37 extending between closed end 33 and generally open end 35. Generally open end 35 is configured to receive drive piston 22 as will be described hereinafter. Plunger body 31 may include vent holes 32 or the like to allow pressure to escape as drive piston 22 is advanced into hollow interior 37. Interior annular groove 39 is provided along the interior surface of plunger body 31 and is configured to receive a radially elastic member as described hereinafter to axially secure plunger 20 relative to drive piston 22. Interior annular groove 39 is desirably provided adjacent generally open end 35, but may otherwise be positioned. Syringe assembly 12 as illustrated in
Referring to
Exterior annular groove 53 is provided about piston body 41 and is configured to receive and retain radially elastic member 60. To assist in retaining radially elastic member 60 therein, exterior annular groove 53 desirably has flattened sides 55 extending generally parallel to one another. Exterior annular groove 53 is desirably positioned toward open end 45, but may be otherwise positioned. Referring to
As illustrated in
With radially elastic member 60 engaged between plunger 20 and drive piston 22, which is controllably axially fixed within casing 7, radially elastic member 60 provides an additional force against axial movement of plunger 20 relative to syringe housing 26. As such, a total force, equal to the friction force plus the elastic member additional force, axially secures plunger 20 relative to syringe housing 26. However, since the elastic member additional force is provided between drive piston 22 and plunger 20, this additional force does not have to be overcome to drive plunger 20 axially inwardly to dispense medication. As such, a more secure positioning between plunger 20 and syringe housing 26 is achieved without requiring a greater drive force.
Alternatively, since the total force includes the elastic member additional force, a reduced friction force may be utilized while still maintaining a desired total force. For example, a prior art system including a seal ring configured to provide a friction force of 2 lbs. between plunger 20 and syringe housing 26 would have a total force of 2 lbs. In an illustrative example of the present invention, elastic member 60, drive piston 22 and plunger 20 are configured such that elastic member 60 provides an additional force of 0.5 lbs. As such, to achieve the same total force, the friction force provided by seal rings 29 between plunger 20 and syringe housing 26 only needs to be 1.5 lbs. Therefore, the total force securing plunger 20 relative to syringe housing 26 remains the same, but the required drive force, i.e., the axial force required to overcome the friction force, is reduced from 2 lbs. to 1.5 lbs. The pump system may be operated more efficiently due to the reduction in the required drive force.
When syringe assembly 12 is to be removed, an axial force opposite arrow A is applied to syringe assembly 12. Radially elastic member 60 again compresses and disengages from interior annular groove 39. To facilitate such, it is desirable that at least rear edge of annular groove 39 has a tapered side wall 57. Both side walls 57 may be tapered. In a desired configuration, opposed side walls 57 are angled relative to one another between approximately 90° and 175°, desirably at approximately 1350 relative to one another. To further ensure that radially elastic member 60 disengages from interior annular groove 39 and not exterior annular groove 53, exterior annular groove 53 is desirably deeper than interior annular groove 39. In a desired configuration, interior annular groove 39 and radially elastic member 60 are configured such that the force required to disengage radially elastic member 60 from interior annular groove 39 is less than the friction force such that the syringe assembly 12 is removed without separating syringe housing 26 from plunger 20.
While specific force values are utilized herein, such values are for illustrative purposes only and are not intended to be limiting. Other configurations with different associated force values are within the scope of the invention.
In the present embodiment, radially elastic member 60 is a canted coil spring 62, as shown in
Referring to
Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.
