Liquid purification or separation – Flow – fluid pressure or material level – responsive – Maintaining stream pressure or flow
Reexamination Certificate
2001-01-23
2003-07-15
Drodge, Joseph (Department: 1723)
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Maintaining stream pressure or flow
C210S086000, C210S097000, C210S109000, C210S201000, C210S207000, C210S253000, C210S258000, C210S305000, C210S320000, C210S522000, C210S532100, C210S259000, C210S436000
Reexamination Certificate
active
06592754
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and apparatus suitable to remove particles from effluent waste, and particularly, to remove amalgam and other metallic particles and other abrasive solids from dental office suction effluent.
BACKGROUND OF THE INVENTION
Although amalgams are less frequently used for new dental fillings than was the case some decades ago, nevertheless, amalgams continue to comprise a significant portion of the metallic particle component of dental office effluent because of the fact that old fillings comprising amalgams are drilled out and removed in the effluent waste when new fillings are effected to replace the old. Further, even under current dental practice, an amalgam is preferred for some tooth filling situations. The use of an amalgam in a filling is never a 100% efficient process; amalgam residues are discharged into the dental office effluent. Typically, dental amalgam comprises a number of metals, invariably of course including mercury and almost always at least some silver. Because mercury is a poison that can accumulate in living tissues and can pose a health hazard to species in a food chain exposed to mercury-containing compounds, and since humans are inevitably at the end of the food chain, it follows that effluent containing amalgams can pose a health hazard to the community at large. Also, certain metals such as silver are commercially valuable if recovered in quantity. For those reasons, it is desirable to devise apparatus and processes for removing amalgams from dental office effluent. In addition to removing amalgams, other matter disposed into dental office suction effluent includes aluminum oxides used in air abrasion treatments and other solid waste material. These solid materials tend to wear out or damage vacuum pumps and other equipment downstream of the dental chair suction apparatus, and also constitute effluent water contaminants. Therefore, it is desirable for the apparatus to remove solid abrasive material and other particulate waste from the dental office suction effluent.
Previously known apparatus for removing amalgam particles from dental office suction effluent are known to include a collecting tank for collecting a working day's accumulation of suction effluent from one or more sources of such waste. The waste is sucked from the dental chair suction apparatus and into the collecting tank by a vacuum pump. When the vacuum pump is turned off, an outlet valve is opened and the accumulated waste is deposited into a separation device intended to separate metal particles from the effluent liquid. Flow into the separation device is induced by the head of fluid in the collecting tank. Particles passing through the separation device are separated from the waste by gravity and settle to the bottom of the separation device. The flow rate is dependent on the head inside the collecting tank; as the head diminishes, the flow rate also diminishes. The changes in flow rate are undesirable because the particle separation rate is affected, and the system becomes prone to plugging when the flow rate decreases. Also, since the waste can be deposited only when the vacuum pump is off, waste is usually moved to the separation device at the end of the day. As a result, the collecting tank and separation device tend to be undesirably large.
Another known apparatus is a centrifuge type system that separates heavier metal particles from effluent liquid by collecting the particles at the peripheral wall of the centrifuge. This apparatus does not effectively separate lighter particles, and is expensive to purchase and operate due to the complexity of its mechanical parts.
Yet another known apparatus uses a dedicated mechanical pump to suction waste liquids through a separator device. Again, a dedicated pump can be expensive to purchase and to maintain, and can be undesirably space-consuming.
Such known systems can become quite complex, unwieldy and expensive, as for example that disclosed in Ralls U.S. Pat. No. 5,885,076 granted Mar. 23, 1999. Ralls teaches the use of sedimentation, co-precipitation and filtration in an expensive complicated apparatus that is probably economical, if at all, only for relatively large installations such as a military base dental complex.
An alternative approach described in Ludvigsson U.S. Pat. No. 5,205,743 granted Apr. 27, 1993 involves provision of an air flow in the vicinity of the patient's mouth and suction from that air flow; such apparatus is designed to remove mercury vapour present in the air flow.
The present invention overcomes some of the shortcomings of the prior technology and achieves further advantages that will be apparent after reviewing the following summary of the invention and detailed description.
SUMMARY OF THE INVENTION
According to the invention, an apparatus is provided for removing metal-containing particles and other waste particles from effluent, particularly effluent from a dental office. While herein the term “metal particles” will frequently be employed, it is contemplated that the apparatus is fully capable of separating other solid particles from effluent liquid. Further, with the aid of one or more precipitants, selected solutes may also be removed. In a particular application to be described in detail, effluent from a dental office suction apparatus is discussed; the metal particles are primarily amalgam particles made of mercury and silver alloyed together in an amalgam composition, sometimes with other metals. The metal particles may be in solid particulate form suspended in the liquid, or may be in solute form dissolved in the liquid. The solid particles other than amalgam residues include aluminum oxides used in air abrasion treatment, enamel and dentin from teeth, porcelain, acrylic used in bridges, and prosthetic cementing agents such as zinc phosphate cement used in crowns and bridges. These solid particles are typically suspended in the liquid effluent. Herein such particles are sometimes collectively referred to as “target particles”, since they are targeted for removal from the effluent. Such target particles also include precipitated particles obtained in the effluent suspension by precipitation of solutes out of solution.
According to one aspect of the invention, an apparatus for removing metal particles and other solid particles from liquid suction effluent can be installed in a dental office using a pre-existing suction/vacuum pump system to provide fluid flow through the apparatus, without requiring dedicated fluid-flow provenance devices. The apparatus may share a common vacuum pump with conventional dental chair suction apparatus, without interrupting the use of suction equipment at the dental chairs.
Removal of solid particles from liquid suction effluent may be effected by a combination of sedimentation and filtration, assisted by flocculation and precipitation. The invention is not concerned with the specific choice of sedimentary deposit apparatus, a preferred implementation being presented herein as a suitable exemplification of such apparatus. Nor is the invention concerned with specific choices of precipitants, coagulants, flocculants, or other associated materials to effect or facilitate removal of solids or solutes; rather, the invention is concerned with the overall system of solids removal, the provision of apparatus and methods for controlling flow of liquids and gases therein, and the facilitation of removal and replacement of deposit tanks that have been filled with solid waste.
In accordance with a preferred embodiment of the invention, the dental office suction effluent is passed from dental chair suction equipment outlets to a surge tank via a suitable inlet port for the surge tank. The surge tank in turn passes effluent into a sedimentary deposit tank, closed on all sides when in use and preferably readily detachable for emptying and replacement. The sedimentary deposit tank in a preferred embodiment has a series of interior walls that separate the interior of the sedimentary deposit tank into a consecutive series of
Barrigar Robert H.
Cecil Terry K.
Drodge Joseph
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