Pumps – Expansible chamber type – Elongated flexible chamber wall progressively deformed
Reexamination Certificate
1999-04-30
2001-05-15
Thorpe, Timothy S. (Department: 3746)
Pumps
Expansible chamber type
Elongated flexible chamber wall progressively deformed
Reexamination Certificate
active
06231320
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a drug infusion pump that employs a pumping cassette, and more specifically, to a mechanism for removably engaging the pumping cassette in a pump chassis.
BACKGROUND OF THE INVENTION
Several different types of pumps are used by medical personnel to infuse drugs into patients. Of these, cassette infusion pumps are often preferred because they provide a more accurately controlled rate and volume of drug infusion than other types of infusion pumps. A cassette pump employs a disposable plastic cassette disposed in the line extending between a drug reservoir and the patient's body. The cassette is inserted into an appropriate receptacle of a pump chassis. The pump chassis provides the driving force that pumps fluid through the cassette and typically includes a microprocessor control programmed to deliver a selected volume of fluid to the patient at a selected rate of flow. In addition, the pump chassis may include one or more pressure sensors and air bubble sensors used to monitor the drug infusion process to protect against potential problems that may arise during the drug delivery.
In prior art designs for the pump chassis, it is common practice to latch a pumping cassette into a receptacle by closing a door over the cassette. When thus closed, the door retains the cassette in a predefined position within the pump chassis. However, the door, its hinges, and its latch tends to add considerable weight and bulk that is a disadvantage in an ambulatory drug infusion system. In at least one prior design for an ambulatory pump chassis, retention of the cassette in its receptacle has required following a four-step process. This prior design employs a sliding cover over the cassette receptacle, with a separate latch for retaining the cassette in the receptacle. Accordingly, to load a cassette into this pump, it is necessary to: (1) press the slide into its open position, (2) open the latch, (3) insert the cassette into its receptacle, and (4) close the slide over the cassette. A corresponding four-step process is also required to remove a cassette from the pump chassis in this pump. Clearly, such a procedure is likely to be considered excessively time consuming and complex when it must be repeated each time that a cassette is engaged in the pump chassis to deliver a drug to a patient.
Thus, it would be preferable to provide a much simpler mechanism for engaging a pumping cassette in a predefined position so that the pump chassis can properly drive the cassette and can monitor pressure and detect any air bubbles in the fluid being administered to a patient. It would be preferable to eliminate any door or slide covering the cassette and to provide a mechanism for unlatching the cassette from the pump chassis with the push of a button. The prior art does not disclose any such mechanism for latching and/or unlatching a cassette in a pump chassis.
SUMMARY OF THE INVENTION
In accord with the present invention, apparatus is defined for engaging a pumping cassette at a predefined position within a pump chassis, for use in delivering fluids to a patient. The apparatus includes a pair of opposed pivotable members disposed at opposite sides of a cavity within the pump chassis; the cavity is sized to receive a pumping cassette. Each opposed member is pivotally mounted to the pump chassis so as to pivot away from and towards the cavity and includes a surface configuration that engages a portion of a pumping cassette, retaining the cassette in the predefined position within the cavity. At least one spring is coupled to the pair of opposed members and applies a biasing force tending to pivot the pair of opposed members towards the cavity. As a pumping cassette is forced into the cavity, interference with the cassette forces the opposed members to pivot outwardly, away from each other and from the cavity. The biasing force causes the surface configuration on each member to engage the pumping cassette after the pumping cassette has been forced into the cavity, retaining the pumping cassette at the predefined position.
A release is also provided, which when activated by an operator, forces the pair of opposed members to pivot outwardly, away from the cavity, thereby releasing a pumping cassette that has previously been inserted and retained within the pump chassis. The release includes a push button that is activated by depressing it, and a tension spring coupled to the push button. The tension spring produces a force tending to bias the push button outwardly from the pump chassis.
The spring that biases the pair of opposed members inwardly preferably extends between the pair of opposed members through the pump chassis.
In one form of the invention, the surface configuration on each of the pair of opposed members includes at least one tab adapted to engage a corresponding slot in the pumping cassette as the pumping cassette is pushed into the cavity. In an alternative embodiment, the tab is adapted to overlie an edge of a pumping cassette as the pumping cassette is pushed into the cavity.
An air bubble sensor is disposed on the pair of opposed members and pivots with them. In this manner, the air bubble sensor is enabled to pivot into contact with a tube connected to a pumping cassette that is retained in the cavity by the pair of opposed members. While not required, in a preferred form of the invention, the air bubble sensors provide an anchor for a spring coupling the pair of opposed members.
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Lawless Michael W.
Scherer Andrew J.
Soberon Peter A.
Squarcia Stephanie R.
Abbott Laboratories
Gartenberg Ehud
Thorpe Timothy S.
Vrioni Beth A.
Woodworth Brian R.
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