Dispensing – Inspection devices
Reexamination Certificate
2002-03-26
2004-05-11
Bomberg, Kenneth (Department: 3754)
Dispensing
Inspection devices
C222S137000, C222S145500, C222S145600
Reexamination Certificate
active
06732887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention is in the field of dispensing devices and, more particularly, in the field of syringe devices configured to mix and dispense mixed compositions.
2. The Relevant Technology
Many reactive compositions are packaged in two parts, often known as “A and B components” or “first and second materials”. Upon mixing, the A and B components undergo a chemical reaction that causes the resultant mixed composition to cure in some desired manner. In the dental field, for example, several mixed compositions currently enjoy wide use, such as cements and composite materials. Dental impression materials are also typically made using multiple components.
In order to function properly, the A and B components should be mixed together rapidly, thoroughly and in the appropriate proportions. Failure to mix the components rapidly can result in loss of valuable working time before the resultant mixed composition cures. In addition, failure to mix the components thoroughly or in the appropriate proportions can result in a composition having less than optimum characteristics. For instance, when a dental cement composition is either poorly mixed or includes the wrong proportions of A and B components, the cement can fail to obtain the chemical strength and/or adhesion properties required for a long-term bond.
One method for gauging and controlling the proportion of A and B components included in the mixed composition is to dispense the components from a pair of single dose syringes containing the appropriate proportions of the A and B components. Once dispensed, the components can then be mixed in a conventional manner, such as with a spatula or another stirring device in a mixing bowl or on a mixing pad. This additional mixing procedure, however, tends to be somewhat messy and time consuming. It is also difficult at times to ensure that the mixing has been sufficiently thorough.
Another method for delivering the A and B components is to use an existing double barrel syringe having two integrally connected syringes and a double plunger assembly for dispensing the contents from the barrels. Double barrel syringes are advantageous for enabling the components to be dispensed more quickly than with single syringes and for ensuring the A and B components are dispensed in the appropriate proportions, particularly when the syringes contain multiple doses. For instance, the double barrels of the syringes can be configured with large storage capacities for containing enough of the A and B components to be used for several doses or applications. Because the barrels are integrally connected, and assuming the plunger assembly is configured to dispense the contents from the barrels simultaneously, the appropriate mixing ratios of the components will be preserved regardless of the amount of the components dispensed from each barrel. The barrels of the syringe can also be coupled to an applicator tip, which is generally useful for initiating and facilitating the mixing of the A and B components inasmuch as the components come in contact within the applicator tip and therefore begin mixing before being dispensed.
One problem with existing double barrel syringes, however, is that they are not configured for being filled from the front or from the barrel tips. In particular, front filling existing double barrel syringes from the front can potentially lead to the introduction of the A and B components into the wrong barrels, because of the small size and proximity of the barrel tips. Introduction of the components into the wrong barrels can be problematic because it can result in premature curing of the components within the barrels. Accordingly, it is necessary to fill existing double barrel syringes that are configured with tips in close proximity from their backsides to avoid mixing the components during the filling process. Backside filling, however, may be undesirable because it can result in the formation of bubbles, air pockets and other pressure irregularities within the barrels which can cause spurting, irregular discharge, or otherwise prevent the A and B components from being dispensed in the appropriate proportions.
Pressure irregularities can also cause cross-migration and the premature curing of the A and B components within the opposing barrels. For example, a bubble existing in the A component barrel will be compressed when an adequate force is applied by the plunger assembly for expressing the A and B components. When the plunger assembly is released, however, the bubble within the A component barrel will expand, thereby forcing the plunger assembly to retract and creating a pressure void within the B component barrel. This pressure void naturally creates a suction force at the tip of the B component barrel which is sufficient to cause some of the residual A component to migrate backwards into the B component barrel where it can prematurely mix with the B component, cure, and inhibit or prevent future use of the syringe.
To avoid the aforementioned problems, some existing double barrel syringes are configured with tips that are spaced far apart so that they can be filled from the front. However, this spacing of the barrel tips also prevents the barrels from connecting with certain applicator tips for mixing purposes, thereby requiring the components to be mixed in an additional step after being dispensed from the barrels and prior to application. As mentioned above, this additional mixing step can be both time consuming and messy. Even if the spaced apart barrel tips are able to be connected to a separate mixing tube or tip, the A and B components must traverse interconnecting pathways existing between the barrel tips and the mixing tip before the components can be mixed, thereby resulting in inefficiencies and wasted product. In particular, the internal volume of the interconnecting pathways between the barrels and the applicator tip represents the volume of the components that will fail to be mixed or discharged from the syringe, and will therefore be wasted.
Yet another problem with integrally connected double barrel syringes is that they are often manufactured out of a single type of material, such as during an injection molding process. This may be economical for manufacturing purposes, but it can also preclude the use of certain inexpensive or desired materials. For instance, by way of example and not limitation, if it is desired to manufacture the syringe out of a transparent material but one component is photosensitive, the double barrel syringe cannot be manufactured out of a transparent material or else the one component will prematurely cure, even when the other component is not photosensitive. Likewise, if the one component adversely reacts with a certain type of material, that certain type of material cannot be used to manufacture the double barrel syringe, even if it will not react with the other component.
Accordingly, in view of the foregoing, there is currently a need in the art for improved dispensing devices and, more particularly, to syringe devices configured to dispense mixed compositions in a quick and convenient manner, while preserving the appropriate mixing ratios of the composition and while reducing any losses associated with transferring the components to an applicator tip. It would also be an advancement in the art to provide such improved syringe devices that have barrels that can be manufactured out of different materials to accommodate the different characteristics of the components that are contained therein.
SUMMARY OF PRESENTLY PREFERRED EMBODIMENTS
Briefly summarized, presently preferred embodiments of the present invention are directed to improved syringe devices that are capable of dispensing the components of a mixed composition in appropriate proportions and of mixing the components prior to being dispensed. The syringe devices of the invention are also configured with tips that can be placed adjacently or in close proximity to reduce any losses associated with transferring the components
Bomberg Kenneth
Nydegger Workman
Ultradent Products Inc.
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