Radiant energy – Irradiation of objects or material
Reexamination Certificate
2002-06-14
2004-03-23
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
C422S022000, C422S024000, C422S028000
Reexamination Certificate
active
06710357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present intervention relates to an improved system for sterilizing articles utilizing ultraviolet radiation.
2. Description of the Prior Art
At present, food packaging products such as dairy product cartons, lids, sealing films, plastic wrap, labels, reusable product containers and other articles used in the packaging of products are sanitized by ultraviolet irradiation. In conventional food packaging and container sanitizing operations the articles to be treated are passed on a conveyor beneath a conventional lamp that emits ultraviolet radiation. The ultraviolet lamp is driven by a magnetic ballast. In order to irradiate and thereby thoroughly sanitize articles on the conveyor system the undersides of the articles resting upon the conveying mechanism must be irradiated, as well as the upper sides.
To irradiate the underside of an article, it has been conventional practice to employ a conveyor belt having an open mesh through which a source of ultraviolet illumination shines. Alternatively, the articles to be irradiated may be placed upon a plurality of narrow, laterally separated belts or chains that support the articles to be irradiated from beneath and convey them through the irradiation tunnel. However, even though both of these conventional systems allow significant portions of the underside of articles transported through the irradiation tunnel to be exposed to ultraviolet radiation, the structures of conventional conveyor systems of this type do cast radiation “shadows” on certain portions of the undersides of the articles being treated. As a consequence, these articles cannot be completely sanitizing by ultraviolet radiation using conventional conveyor systems.
A further difficulty in sanitizing articles conveyed past an ultraviolet irradiation source is that the presence of surfaces parallel to the rays of the irradiation source and also indentations and other nooks and crannies in the articles prevents the ultraviolet radiation from striking all of the surfaces of the articles. Consequently, bacteria can linger untreated in areas on the surfaces of the articles that do not receive direct or reflected ultraviolet radiation.
Still another problem that exists in conventional ultraviolet irradiation tunnels is that the lamps emitting the ultraviolet radiation tend to deteriorate rather rapidly, particularly if they are constructed as elongated tubes. Nevertheless, an elongated tubular shape for the ultraviolet irradiation sources is the best shape for irradiating the entire width of the irradiation tunnel.
The problem that arises is that conventional ultraviolet radiation lamp tubes are supported at their ends, but are unsupported between their ends. Any support between the ends of the tubes would interfere with the radiation emitted. As a consequence, with the intense heat that is built up in the generation of ultraviolet radiation, the tubular structure of the ultraviolet radiation lamps softens and tends to sag at the centers of the lamps. When this occurs radiation is irregular and at a reduced intensity. Also, this deformation of the bodies of the tubes causes structural damage, leading to premature failure of the ultraviolet radiation lamps. The longer the tubes, the greater the likelihood of damage in this connection. Some ultraviolet tubes can have a length as great as 10 feet.
To solve this problem it is conventional practice to periodically rotate the elongated ultraviolet radiation tubes one hundred eighty degrees to reduce the distortion to the structure of the lamp tubes caused by sagging at their centers. This maintenance procedure does prolong the life of the lamp, but requires the combined effort of two persons to rotate each lamp. That is, the supports at both ends of the ultraviolet radiation lamp tubes on both sides of the tunnel must be accessible. This is often difficult or inconvenient, since one side of the tunnel may be located close to a wall of a room in which the tunnel is located. In any event, the individuals performing the task must coordinate their efforts and simultaneously remove the ends of the lamp tubes from their supports and rotate the ends of the tubes one hundred eighty degrees. The ends of the tubes must then be replaced in their supports. This maintenance process is therefore rather time-consuming and requires two people.
SUMMARY OF THE INVENTION
The present invention provides an improved system for irradiating articles with ultraviolet radiation within an irradiating tunnel that largely solves the foregoing problems. The system of the present intervention greatly reduces or eliminates completely the problem of “shadows” being cast upon portions of the articles as they are conveyed through the tunnel. The system of the invention also provides a construction that allows a single person to rotate an ultraviolet radiation tube one hundred eighty degrees and reseat it in its support. The unique system of the invention greatly improves the degree of sanitation that is achieved using ultraviolet radiation upon articles conveyed past an ultraviolet irradiation source.
The invention involves a system for irradiating generally flat or collapsible objects such as reusable produce shipping boxes and food packaging materials that have various crevices, openings, and other niches in which bacteria can collect, or even just surfaces that are perpendicular to the path of travel of the articles through the tunnel. In conventional systems in which the objects are transported on a conveyor chain, there is always a “shadow” cast by the conveyor chain or drive on the undersides of the items being irradiated as the articles are transported through an irradiation tunnel. These shadows prevent the article from being completely irradiated.
According to the improvement of the invention, the drive chains or belt system upon which the objects are supported is divided into segments in which the conveyor chains or belts of each sequential segment are laterally offset from the conveyor chains of the adjacent conveyor segment or segments. Thus, although a conveyor chain or belt of one segment will cast a shadow on the location of the underside of the article to be irradiated, the shadows are cast upon a different part of the article in the next sequential segment. As a consequence, as the object passes through the tunnel, at one point or another the entire undersurface, as well as the upper surface, is irradiated so that there is no sheltered, shadowed region on the underside of the articles being conveyed. To the contrary, all areas of the undersurface of the article are exposed to ultraviolet radiation sometime during the progression of the article along its path of travel.
A further feature of the invention is the use of nonparabolic reflectors, such as elliptical reflectors. In conventional practice the elongated, tubular ultraviolet radiation lamps are located above and beneath a conveyor system. To maximize the ultraviolet radiation directed at the articles being transported by the conveyor system each elongated ultraviolet lamp is provided with a concave reflector located behind the lamp and facing the articles being transported through the irradiation tunnel. The axis of the lamp is located within the arc of curvature of the reflector. It has been accepted practice in conventional practice for the reflectors to be constructed with a parabolic cross section. As a consequence, ultraviolet radiation that is reflected from the conventional parabolic reflectors travels in parallel paths to impinge upon articles passing on a conveyor system therebeneath.
While such a construction does provide for reflection along the shortest path to reach the article, the fact that the reflected radiation travels in parallel rays means that the reflected radiation is always directed at the article perpendicular to its path of travel. Consequently, surfaces of the article that are oriented perpendicular to the path of travel receive little, if any radiation. The same is true of indentations, niches, slots, and under
Gill Erin-Michael
Lee John R.
UV Doctor LLC
LandOfFree
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