Dispensing – Resilient wall – Supply container delivering to receiving chamber
Reexamination Certificate
2000-07-06
2001-06-12
Jacyna, J. Casimer (Department: 3751)
Dispensing
Resilient wall
Supply container delivering to receiving chamber
C222S214000, C222S187000, C222S325000, C222S450000
Reexamination Certificate
active
06244474
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an improved pump mechanism for dispensing small aliquots of a liquid, such as a biological reagent. It may serve as part of an apparatus which dispenses a plurality of reagents to be dispensed in small volumes.
Current methods for dispensing reagents generally use pumps which require the priming of tubing lines leading into and out of a pump. When the pumping is finished, the tubing lines must be flushed before a different reagent can be pumped, lest cross-contamination of reagents occur. Because of the need for priming and clearing tubing lines, such types of pumps are not easily interchangeable.
Pumping systems using a syringe housing (“syringe pumps”) are well known to those in the field. The liquid can then be accurately dispensed by applying a precise pressure on the plunger, usually by an electromechanical actuator. The distance that the plunger is depressed directly controls the amount of fluid to be dispensed. Such syringe pumps have two advantages: 1) the absence of tubing lines leading into and out of a pump which must be primed and flushed, and 2) the separation of the wetted components from the electromechanical controlling elements.
Such syringe pumps are useful in situations where repetitive dispensing of precise amounts of liquid are required. A drawback of such syringe pumps is that interchanging syringes on a single electromechanical actuator requires that the actuator mechanism be realigned with the position of the syringe plunger that is being inserted. In circumstances where the syringes need to be changed often in order to change the dispensed reagent, the need for repetitive manual intervention to align the electromechanical actuator with the position of the syringe plunger is a disadvantage.
A modified form of syringe pump is presented in U.S. Pat. No. 4,844,868 to Rokugawa and U.S. Pat. No. 5,232,664 to Krawzak et al. In those devices, liquid is drawn into a syringe from a reservoir through a check valve and then dispensed through a second check valve. Unfortunately, the increased complexity of sliding seals, valves with balls and springs and multiple parts to be assembled renders such designs relatively costly to manufacture. This is a particular disadvantage where the liquid dispenser is meant to be disposable.
U.S. Pat. Nos. 5,645,114 and 5,316,452 to Steven A. Bogen and Herbert H. Loeffler and assigned to the Assignee of this invention prevent a liquid dispensing pump comprising a metering chamber attached to a liquid reservoir. The reservoir is a syringe barrel, sealed at the top by a moving plunger. As liquid is dispensed, the plunger moves progressively deeper into the reservoir/syringe barrel. The plunger thereby serves to exclude air and prevent spillage of the liquid contained within the reservoir. The metering chamber comprises a flexible housing with two unidirectional duck-billed valves. As the housing is compressed, liquid is ejected out of the chamber through the lower valve. As the compression force is released, the flexible housing resumes its native (expanded) state, thereby drawing liquid into the housing from the reservoir.
By positioning a plurality of such liquid dispensers on a moving platform, a single electromechanical actuator can selectively dispense from a variety of dispensers. In this manner, the cartridge pumps are interchangeable.
SUMMARY OF THE INVENTION
The present invention relates to an improvement in the liquid dispenser presented in the Bogen et al. patents. In particular, it presents a liquid dispenser which uses novel valves to provide more consistent operation. The novel valves have more reproducible cracking pressures, minimize the formation of drops at the dispenser outlet and provide more controlled flow of liquid ejected from the dispenser.
In a preferred embodiment, a cartridge pump comprises a liquid reservoir for containing a liquid, such as a biological or chemical reagent. The reservoir has a liquid flow outlet at the bottom thereof to which a metering chamber is directly connected. The metering chamber comprises a compressible housing having a non-compressed shape. A one-way inlet valve and a one-way outlet valve are provided at respective ends of the compressible housing and are aligned in the same direction to allow unidirectional flow from the reservoir through the housing. The compressible housing may be compressed for the unidirectional ejection of a volume of liquid from the metering chamber. The compressible housing returns to the non-compressed shape after cessation of compression to draw an additional volume of liquid into the metering chamber from the reservoir.
The cartridge pump may be attached onto a moving platform by means of a feature on the side of the cartridge pump. The mating receptacle for the feature is on the moving platform. The moving platform actually contains a multiplicity of suitable attachment sites for cartridge pumps, allowing it to carry a multiplicity of liquids. By moving the platform so as to position a desired cartridge pump adjacent to an electromechanical actuator, the instrument can select which liquid will be dispensed. If a different chemical or biological procedure is subsequently required, the cartridge pumps can be replaced with other cartridge pumps containing the necessary reagents for the new procedure. Therefore, the cartridge pump design allows an instrument to be extraordinarily versatile.
A novel valve design is incorporated into the preferred liquid cartridge pump dispenser. The valve features a high seating force and a lower, moderate opening (“cracking”) force, facilitating leak-free operation. In particular, each check valve at the inlet and outlet of the compressible elastomeric housing of a metering chamber comprises a flexible membrane having an aperture. A valve seat fixed to the housing seats into the aperture of the flexible membrane and causes the flexible membrane to be deformed. The deformed flexible membrane has an elastic restoring force which causes the membrane to act upon the valve seat to provide a positive liquid seal. Preferably, the valve seat is conical and extends from a rigid disk. The preferred outlet check valve further includes a guidepost extending from the conical valve seat and a tubular nozzle extending from the flexible membrane about the aperture and the guidepost. It is preferred that at least one of the membranes be formed as a unitary part with the compressible elastomeric housing.
Preferably, at least the liquid reservoir is pivotably mounted in a rigid plastic housing with the metering chamber suspended from the reservoir. As the electromechanical actuator drives a compression member to compress the meter chamber against a fixed back-supporting surface, the reservoir and housing tilt slightly. As the dispenser tilts within its rigid plastic housing, the metering chamber receives compression force that is distributed between the front (by the compression member of the electromechanical actuator) and the back (by the fixed back-support), thereby avoiding kinking and bending of the housing and the resultant unpredictable directions of dispense. This tilting feature also results in a slight arc in the path of dispensed liquid, an advantage if the liquid needs to be spread out over a surface. Moreover, the tilt allows the fluid stream to interrupt a fixed optical beam, for detection of liquid dispense.
The preferred reservoir is formed from a flexible plastic bag. The reservoir may be connected to the metering chamber prior to filling by means of a mechanical joint. A small hole at the bottom of the bag is positioned over a larger hole at the top of the metering chamber fluid inlet valve. A cylindrically-shaped hollow plug is then pressed into the aligned holes from above, causing the two apertures to seal to each other. The reservoir (in the form of a flexible bag) may also be joined to the metering chamber inlet by other means, such as by the application of heat, ultrasonic, RF, or adhesive sealing methods. In addition, the liquid reservoir may be made of a unita
CytoLogix Corporation
Hamilton Brook Smith & Reynolds P.C.
Jacyna J. Casimer
LandOfFree
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