Electric lamp and discharge devices: systems – Pulsating or a.c. supply
Reexamination Certificate
1999-12-07
2001-07-24
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
C315S2090SC, C315S291000, C315S046000, C210S748080, C210S243000
Reexamination Certificate
active
06265835
ABSTRACT:
BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION
In a typical fluid treatment purification system utilizing ultraviolet (UV) energy, the fluid, which may be a liquid and/or gaseous substance contaminated by pathogenic organisms is moved through a treatment zone. Typically, the UV energy is provided by causing a discharge in a gaseous medium contained in a UV transmissive bulb or envelope. Typical gas fillings include mixtures of argon (and/or other gases such as xenon XE, krypton KR) and mercury which, upon discharge therein, is rich in ultraviolet (other UV rich gases on ionization may be used). Typically, a ballast power supply is connected to the electrodes. In electronic ballast systems, a step-up transformer provides a high striking or ionization voltage, several hundred volts (which, once the lamps are energized, is lowered to a normal operating voltage (normally in the range of 100-200 volts)).
When the ultraviolet lamps are used for large scale water purification and treatment systems, the lamps, typically a cylindrical ultraviolet ray-emitting lamp and an outer coaxial and substantially coextensive cylindrical UV transparent sleeve, are arranged in banks or arrays in parallel rows. Various structural arrangements are utilized to enable and facilitate the mounting of the banks or arrays of UV lamps in a water-flow conduit for treatment of the water. Typically, the axis of the UV lamps are parallel to the flow direction of the water.
In some systems, the UV source is driven in two or more intensity modes, a low intensity mode when the fluid flow is low and a high intensity mode when the fluid flow is high. Reference is made to the following prior U.S. patents:
U.S. Pat. No.
Issued
Inventors
4,482,809
11/1984
Maarschalkerweerd
4,872,980
10/1989
Maarschalkerweerd
5,023,518
06/1991
Mans et al
5,081,399
01/1992
Jy
5,230,792
07/1993
Sauska et al
5,324,423
06/1994
Markham
5,401,395
03/1995
Markham
5,503,800
04/1996
Free
5,536,395
07/1996
Kuennen et al
5,547,590
08/1996
Szabo
5,611,918
03/1997
Markham
5,698,091
12/1997
Kuennen et al
5,707,594
01/1998
Austin
Sauska et al U.S. Pat. No. 5,230,792 and Markham U.S. Pat. No. 5,611,918 are typical examples of ultraviolet water purification systems with variable intensity controls. In these patents, the intensity of an ultraviolet lamp is controlled by a circuit which is responsive to fluid flow for selectively energizing the lamp to provide variable UV intensity output depending upon fluid flow. In these circuits, a high striking voltage is required to initiate the discharge and produce ultraviolet. In the case of Sauska et al, the circuit arrangement is such that the ultraviolet lamp is always started with a high-current ballast. This is in order to assure the striking of a discharge, and then a low-mode ballast is used to maintain the UV lamp in the low output stage status.
THE PRESENT INVENTION
The object of the present invention is to provide an improved ultraviolet energy source and, more particularly to provide a ballast-free energy-efficient ultraviolet energy source, and still more particularly to provide such a UV source in a fluid treatment system and yet more particularly to provide a significantly more efficient, low-current, ultraviolet light-producing system for treatment of various fluids and substances and materials and water treatment useful in killing and/or controlling pathogens, microorganisms, bacterial and other deleterious materials in flowing fluid systems such as water purification and air purification systems.
The UV energy produced by the invention can be used for curing, UV medical treatments and diagnostics, tanning salons, photolithographic applications, signalling systems, imaging systems enhancing chemical reactions, detection systems, destruction of undesired vegetation, optical recording systems, insect attractants, in situ dental, etc.
Since the ultraviolet energy source of the present invention is significantly lower in power consumption and produces significantly more useful ultraviolet energy/per watt than conventional ultraviolet energy lamps and bulbs that it replaces, fewer lamp units for a given treatment may be required; and since there is no heated filament, the lamps have longer lifetimes. In addition, since the intensity level can be varied from zero to high intensity and back to zero in an infinitely variable manner, the intensity rate of the ultraviolet energy can be varied in a likewise infinitely variable manner (e.g. step-less variations).
Since heated filaments are not utilized, the device is essentially non-thermionic.
According to the invention, one or more ultraviolet lamps are started and operated from an alternating-current square-wave power supply driver circuit. The square-wave power supply driver circuit incorporates a solid state switch circuit which is operated to generate a substantially square-wave alternating-current voltage at the ultraviolet lamp or tube electrodes, such that the square-wave alternating-current voltage applied to the electrodes reverses polarity more rapidly than the pattern of electron and ion density in the UV tube can shift so that electrons throughout the length of the space between the electrodes are continually accelerated and will, through several cycles of the applied square-wave voltage, create free electrons and ions throughout the tube volume and ionize the gas-producing ultraviolet energy in a discharge. In the preferred embodiment, the oscillating frequency is set in the range from about 100 kHz to about 1.5 MHz and, more precisely, between 1 MHz and 1.5 MHz. In preferred embodiments, there are no high voltages in the driver circuit so safer operation is assured. Variation in intensity levels can be achieved by varying the voltage or energy level from the direct current supply to the driver circuit. In a preferred embodiment, care is taken to assure that there are no spike voltages due to inductive kicks and the like. Since the ultraviolet lamps or devices are non-thermionically driven, e.g. the filaments are not heated, the efficiency of UV production is significantly improved. Moreover, at the high-frequency range, the power supply can be much smaller.
Another feature of the present invention is that in comparison to traditional ultraviolet lamp systems there is marked reduction in current, power consumption and heat, accompanied by significant increase in ultraviolet light energy output which, in turn, is the reason why efficient conversion of electricity to ultraviolet energy is high. Some of the heat (power) reduction is, of course, recognizable as resulting from the absence of direct heating of the filaments in each end of the tube by applied voltages. Some is also explained in terms of energy transfer in the high-field region which occurs near the momentary cathode. However, ultraviolet lamps in the system of the present invention are much cooler throughout their length including areas that are the greatest distances from the filaments or electrodes whose heating could not possibly be explained by conduction, radiation or diffusion heat transferred through the low pressure gas filling the tube. The alternating-current square-wave AC at about 75 kHz to about 1.5 MHz with the preferred range being about 1.0 MHz to about 1.5 MHz depending in part on the atomic particles (of a given gas discharge medium).
Cooling along the length of the tube is believed to be explainable in terms of energy transferred to electrons and ions by the applied electric field. In the present invention, the square-wave applied voltage to the tube reverses so frequently that positive ions in the discharge can build up little kinetic energy during a half-cycle of the applied voltage. In conventional ultraviolet lighting systems driven by discharge (e.g. non-microwave or magnetron driven UV system), larger amounts of energy can be acquired by ions in one-half cycle. This kinetic energy contributes nothing to ultraviolet light production, but in conventional systems is rapidly transferred to neutral gas molecules and thence to the walls of the tube.
A major sour
Vo Tuyet T.
Wong Don
Zegeer Jim
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