Radiant energy – Supported for nonsignalling objects of irradiation – With source support
Reexamination Certificate
1998-11-25
2001-07-31
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Supported for nonsignalling objects of irradiation
With source support
C250S454110, C250S50400H, C210S232000, C422S186300
Reexamination Certificate
active
06268607
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field
This invention relates to the use of UV light for the purification of air and water. It is particularly directed to apparatus and methodology specifically useful in clinical surroundings, notably dental operatories.
2. State of the Art
Ultraviolet (UV) radiation has been widely investigated for its potential utility in air and water purification applications. The portion of the electromagnetic spectrum having wave lengths between about 1000 and about 4000 Å (angstrom units) is conventionally referred to as “ultraviolet light,” even though it is not visible to the human eye. An angstrom unit is one ten billionth of a meter. The UV spectrum is alternatively defined as comprising wavelengths between about 100 and about 400 nm (nanometers). The UV portion of the spectrum is further arbitrarily divided into three band widths; specifically: UV-A (long-wave, above 320 nm), UV-B (medium wave, between about 280 and about 320 nm) and UV-C (short-wave, between about 100 and about 280 nm). UV-C radiation has been found to possess the greatest germicidal effectiveness, a wave length of 253.7 nm being commonly referred to as “germicidal UV.”
UV-C radiation has been used commercially for air purification. U.S. Pat. No. 4,422,824, for example, discloses a ceiling fan with blades housing germicidal (UV) light bulbs. The blades are structured with chambers to direct air past the lights, thereby exposing airborne micro-organisms to UV light.
The germicidal effectiveness of UV-C radiation against both air-borne and water-borne microorganisms is discussed in the article “Ultraviolet Water Purification,”
Pollution Engineering Magazine,
Vol. 5, No. 12, December, 1973. This article, the disclosure of which is incorporated by reference as a portion of this specification, describes practical constructions of germicidal lamps and water purification systems utilizing such lamps. Modem UV water treatment systems are disclosed by U.S. Pat. Nos. 5,401,394 and 5,536,395. The article, “Applications for Ultraviolet,” Ann M. Wysocki,
Water Conditioning and Purification Magazine,
May 1988, describes a water purifier and proposes a number of practical applications for such a device. This article, which is incorporated by reference as a part of this specification, also details a set of criteria for an acceptable ultraviolet disinfecting unit.
One important consideration in the utilization of UV radiation in a space normally occupied by humans, is the safe exposure limit to such radiation. The National Institute for Occupational Safety and Health (NIOSH) has adopted as “safe” an exposure below the level found to cause eye irritation. In the case of germicidal UV (253.7 nm), the safe exposure limit is less than 0.2 &mgr;watt/cm
2
over any eight-hour period.
UV light has apparently not found practical application in dental operatories for air and water purification. U.S. Pat. No. 5,204,004 discloses a water line filtration system for dental operatories. The system is designed to prevent water flowing through a supply line to a hand piece from carrying bacterial contamination into a patient's mouth. The biofilm which normally forms in such a supply line is identified as a source of bacterial contamination for dental patients. U.S. Pat. No. 5,556,279 discloses a water purification system for dental instruments. The system is typical of equipment found in dental operatories, and consists of a disposable cartridge element comprising activated carbon and exchange resins disposed in a water supply line.
BRIEF SUMMARY OF THE INVENTION
A dental office is provided with a system to purify air and/or water delivered to the operatory. Purification is by means of UV-C light applied to the utilities as they are transported from supply to delivery sites. Ideally, the system includes separate devices structured and arranged to effect purification of the ambient air circulating within the operatory, the water supplied to the operatory and the water delivered to and through dental hand pieces in connection with a procedure.
The devices relied upon for ambient air and normal utility water purification may be patterned after conventional UV systems, but sized and configured appropriately to assure adequate biocidal activity within the safe exposure limit for humans. A special purpose device is provided for the purification of water delivered through a dental delivery system. This device comprises a simple in line purifier and requires no special controls, valves or plumbing.
As presently contemplated, this invention may be embodied as a water purification system for a dental operatory. The system may be supported by a mounting bracket suspended from the support structure of a dental delivery system. Mounting structure associated with the mounting bracket will generally include reservoir support structure, germicidal bulb support structure, and quartz tube support structure. A water reservoir is typically suspended from the reservoir support structure in fluid-tight association with that structure. A germicidal UV bulb will be suspended from the germicidal bulb support structure, approximately coaxially with the reservoir, which is typically, but not necessarily, shaped as a cylinder with a circular cross section. The bulb will in most cases have a first end proximate the support structure and a second end remote from the support structure. A quartz tube may be held by the quartz tube support structure, approximately coaxially with the germicidal UV bulb. An inlet, usually associated with the support structure, is structured and arranged to deliver water to the interior of the reservoir near the second end of the bulb. An outlet, also usually associated with the support structure, is structured and arranged to receive water from the interior of the reservoir from a location near the first end of the bulb.
In general, the in line purifier of this invention may conveniently be constructed and arranged for mounting to a dental support post of the kind conventionally present in a dental operatory. Alternatively, the purifier may be mounted from a wall or a frame structure in the proximity of a dental delivery unit. In any case, the purifier is generally suspended from a mounting bracket structured as required to interface with the support structure selected for a specific installation. A reservoir, such as a tank, is suspended from the post or other support structure, usually in approximately parallel orientation, and contains a supply of water as well as the germicidal components of the system. An inlet provides water to the reservoir, ideally near its bottom. Water is displaced upwardly through the reservoir, eventually exiting through an outlet at its top. The volume of the reservoir is selected to assure a specified minimum dwell time of water in the reservoir as it flows through the system under peak use conditions. The dwell time should be sufficient to permit a germicidally effective exposure to UV light of the water during peak use conditions. A reservoir volume of about 10 to about 40 cubic inches constitutes the operable range for most dental applications, with volumes between about 15 and about 35 cubic inches constituting the preferred practical range, based upon the usual water volume requirements of such operatories.
UV light may be provided by means of an elongate germicidal UV bulb suspended within a quartz tube mounted approximately coaxially with the bulb and the reservoir. The annular volume thereby formed between the quartz tube and the interior wall surface of the reservoir functions as a treatment zone. Water is introduced to the bottom of this zone, assuring that it travels the full length of the UV bulb to reach the outlet at the top of the zone. In this fashion, maximum UV exposure of the water is assured.
The reservoir tank and quartz tube require periodic cleaning. They are thus preferably associated through structural means which permit removal of these components without disconnecting water lines at the inlet and outlet. Ideally, the quartz tube is removable w
Hanson Richard W.
Marsh Leonard
Radicone Michael
DCI International, Inc.
Nguyen Kiet T.
TraskBritt P.C.
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