Plug and method of manufacture

A plug for an enclosure for holding a radiation source is provided. The plug is formed from a material that emits visible light when the radiation source is energized, such that the status of the radiation source may be determined by an operator without the need for status monitoring equipment. The plug seals the radiation source from the environment to prevent ozone formation and to prevent leakage into or out of the enclosure.

FIELD OF THE INVENTION
 The present invention relates to a plug and method of manufacture of a
 plug, and more particularly to a lamp plug operable to indicate instances
 when a radiation source is energized.
 BACKGROUND
 Treatment systems and techniques for removing contaminants from
 contaminated media (such as liquids, gasses, and solids) have been
 developed in the past. Such conventional treatment systems and techniques
 include treatments using ultraviolet radiation. Contaminated media are
 often exposed to ultraviolet radiation permitted by radiation source, such
 as an ultraviolet lamp, which causes contaminants in the media to become
 inactive or to be reduced or oxidized.
 Although ultraviolet radiation treatment is an effective way to
 decontaminate contaminated media, several problems have been encountered
 with ultraviolet radiation treatments.
 One problem is that ultraviolet lamps must be monitored in order to replace
 the lamps when they fail. An automated monitoring system may be used, but
 such systems typically require extensive wiring, metering, and controls.
 Automated systems are typically not utilized to their full potential
 because lamp failure does not need to be immediately detected. Thus, an
 automated system provides a higher level of monitoring than may be
 required, usually at a significantly greater cost.
 Another problem encountered with ultraviolet radiation treatment systems is
 the generation of ozone. Because such systems are generally exposed to
 environmental oxygen, ozone is formed when the system is in operation. In
 an enclosed location, such as an indoor facility, such systems can
 generate potentially dangerous levels of ozone and must therefore be well
 ventilated.
 Another problem encountered with ultraviolet radiation treatment systems is
 the breakage of the enclosures in which ultraviolet lamps are disclosed.
 Glass enclosures typically seal ultraviolet lamps from liquid media, and
 may be subject to hydrostatic pressures. When glass enclosures break, the
 leakage of the liquid media from the system may result in a hazardous
 condition.
 SUMMARY OF THE INVENTION
 Therefore, a need has arisen for a lamp plug and method of manufacture that
 allows the status of a lamp to be monitored without the need for active
 monitoring equipment.
 In accordance with the present invention, a lamp plug and method of
 manufacture are provided that overcome problems inherent with known
 methods for monitoring lamp status.
 One aspect of the present invention is a plug for an enclosure in which a
 radiation source, such as an ultraviolet lamp, is disposed. The plug is
 formed from a material that emits visible light when the radiation source
 is energized, such that the status of the radiation source may be readily
 determined by visual inspection and without the need for monitoring
 equipment. The plug also operates to seal the radiation source from the
 environment to prevent ozone formation and leakage into or out of the
 enclosure.
 Another aspect of the present invention is an apparatus for holding a
 radiation source. The apparatus includes an external housing made of a
 transparent or translucent material. The external housing has at least one
 opening through which the radiation source may be inserted into the
 external housing. A plug is installed in the external housing that seals
 the opening of the external housing. The plug is made of a material that
 emits visible light when the radiation source is energized. One or more
 conducting elements are installed through the plug, which allow the
 radiation source to be electrically connected to an external power source.
 Another aspect of the present invention is a method for decreasing ozone
 generation in a decontamination system. The method of the present
 invention includes placing each of two or more radiation sources in a
 corresponding enclosure. Each enclosure is sealed with an airtight
 translucent plug that emits light when the radiation source is operating.
 Each radiation source is electrically connected to a power source using a
 conductor that is installed through an airtight penetration of each
 airtight translucent plug.
 Yet another aspect of the present invention is a method for manufacturing a
 plug for an enclosure that holds a radiation source. The method includes
 forming a plug from an ultraviolet-sensitive material having predetermined
 dimensions. A seal structure is then formed onto the plug, and a
 penetration is formed through the plug. A conductor is installed through
 the penetration in a manner so as to maintain an atmospheric seal.
 The present invention provides many important technical advantages. One
 important technical advantage of the present invention is a passive status
 indicator for lamp functionality in a decontamination or disinfection
 system. The present invention utilizes material properties of
 ultraviolet-blocking or ultraviolet active materials to provide an
 indication of the operational status of a radiation source without
 requiring electronic monitoring equipment.
 Another important technical advantage of the present invention is a method
 for preventing the formation of ozone in a disinfection or decontamination
 system. The present invention uses a plug that indicates the operability
 of the radiation sources of the system, thus allowing the system to be
 sealed without requiring expensive and complex monitoring equipment. The
 method of the present invention thus limits ozone formation while allowing
 the status of the radiation sources to be easily monitored.

DETAILED DESCRIPTION OF THE DRAWINGS
 The following description, with reference to the accompanying drawing,
 details a preferred embodiment of the presention. It should, however, be
 appreciated that the present invention may be embodied in numerous other
 embodiments.
 FIG. 1 is a diagram of a lamp plug assembly 100 in accordance with a
 preferred embodiment of the present invention. Lamp plug assembly 100 may
 be used to seal an enclosure, such as a quartz tube, in which a radiation
 source, such as an ultraviolet lamp, is disposed. The radiation source
 may, for example, be used to disinfect or decontaminate an aqueous or
 gaseous media.
 Lamp plug assembly 100 includes plug 102, o-ring seal 104, and plug nut
 106, all of which fit into enclosure 108. As shown, plug nut 106 is
 threaded with threads 118 and mates with threads 116 of enclosure 108. By
 applying a tightening torque to plug nut 106, a sealing pressure is
 exerted against plug 102, o-ring seal 104, and plug seat 114 of enclosure
 108. In this manner, an airtight and water tight seal may be formed to
 prevent water or air from circulating beyond the seal formed by plug 102
 and o-ring seal 104.
 Plug 102 is preferably formed from a material that is ultraviolet luminous
 or ultraviolet blocking. For example, plug 102 may be formed of
 polycarbonate, such as by machining a cast polycarbonate block or
 polycarbonate rod. Polycarbonate material absorbs ultraviolet radiation,
 but allows visible light radiation to pass through. Thus, the visible
 light generated by an ultraviolet lamp or other suitable radiation source
 will transmit through plug 102, whereas the ionizing ultraviolet radiation
 will be blocked. Also or alternatively, plug 102 may be formed of a
 material that is ultraviolet luminescent. For example, plug 102 may
 comprise a polymer, epoxy, plastic, or other suitable material that is
 ultraviolet luminescent, or that contains a filler that is ultraviolet
 luminescent. The ultraviolet luminescent material will absorb ultraviolet
 light and emit visible light. Thus, when an ultraviolet lamp disposed in
 enclosure 108 is active, plug 102 will emit visible light.
 Plug nut 106 includes cable and viewing penetration 120. Cable and viewing
 penetration 120 provides an opening to plug 102 through which cable 110
 extends so as to allow an operator to view the status of plug 102.
 Cable 110 includes conductors 126 and 128. Cable 110 is used to provide
 electric power to the ultraviolet lamp contained within enclosure 108.
 Cable 110 extends through plug 102 and cable penetration 124, and the
 jacket of cable 110 may be used to form an environmental seal. Cable 110
 may alternatively comprise a penetration assembly that is configured to
 rotate freely from plug 102, such that plug 102 may be rotated without
 placing a torque on cable 110. Other suitable configurations may be used
 to provide for the penetration of plug 102 with cable 110.
 Plug 102 includes o-ring seal seat 112. O-ring seal seat 112 may be
 machined onto plug 102 during the manufacturing machining of plug 102.
 Also or alternatively, if plug 102 is formed by injection molding or other
 suitable processes, o-ring seal seat 112 may be formed as part of the
 injection molding process.
 Enclosure 108 includes plug seat 114 and threads 116. Plug seat 114 is a
 suitable chamfered region in enclosure 108, such that a force may be
 applied to plug 102 and o-ring 104 in order to form a seal against the
 chamfered edge of enclosure 108. In this manner, a pressure differential
 may exist between the interior and exterior of enclosure 108 without
 allowing liquids or gasses to pass through the seal created by plug 102,
 o-ring seal 104 and enclosure 108. This seal may be used to contain
 liquids within enclosure 108 in the event of a catastrophic failure of
 enclosure 108, or to prevent ozone and other harmful materials from
 leaving enclosure 108 if they are formed during normal irradiation
 processes.
 In operation, lamp plug assembly 100 is used to seal an enclosure that
 holds an ultraviolet lamp or other suitable radiation source that may be
 used for disinfecting and decontaminating a gaseous or liquid media. Plug
 102 is formed of a material that emits visible light and blocks harmful
 ultraviolet radiation or other harmful radiation, such that an operator
 may determine the operational status of the lamp contained within
 enclosure 108 by observing the plug 102 through cable and viewing
 penetration 120 of plug nut 106. Cable penetration 124 allows cable 110 to
 enter enclosure 108 and provide power to the ultraviolet lamp or other
 energy source without allowing moisture or air to enter or exit enclosure
 108. In this manner, ozone formed by the action of the ultraviolet lamp or
 other energy source within enclosure 108 may not exit and is contained
 within enclosure 108, thus maintaining the safety of the work environment
 external to enclosure 108. In addition, if enclosure 108 is used to seal
 the ultraviolet lamp from a gaseous or aqueous media, o-ring seal 104
 prevents catastrophic failure of enclosure 108 from resulting in leakage
 of the gaseous or aqueous media into the external environment.
 FIG. 2 is a diagram of an enclosure plug assembly 200 in accordance with a
 preferred embodiment of the present invention. Enclosure plug assembly 200
 includes plug 202, enclosure 108, and o-ring seal 104. Plug 202 fits
 within interior of enclosure 108, and is held in position by o-ring seal
 104. In this manner, plug 202 forms a seal against enclosure 108.
 Plug 202 may be formed from similar materials and using similar processes
 as plug 102 of FIG. 1. For example, plug 202 may be formed by machining a
 polycarbonate or other ultraviolet blocking material, or by injection
 molding of an epoxy, polymer, plastic, or other material that is
 ultraviolet luminescent or that contains ultraviolet-luminescent filler
 material. O-ring channel may be formed by machining, by an injection
 molding process, or by other suitable processes such as a combination of
 injection molding and machining. Cable 110 extends through cable
 penetration 124' into the interior of enclosure 108. Cable penetration
 124' may be a fixed penetration, such that the jacket of cable 110' forms
 an airtight seal, or may be an airtight penetration assembly that allows
 cable 110' to rotate about an axis such that plug 202 may be turned
 axially. Cable penetration 124' may also or alternatively comprise two or
 more penetrations, as suitable.
 In operation, enclosure plug assembly 200 may be used to provide a seal for
 an enclosure 108 that is not required to be maintained against significant
 differential pressure variations. For example, plug 202 may be used where
 the ambient pressure differential between the outside of enclosure 108 and
 the inside of enclosure of does not exceed a predetermined value, such as
 one-tenth of one atmosphere. This predetermined value is determined by the
 seal force that may be applied by o-ring seal 104.
 FIG. 3 is a diagram of a decontamination system 300 in accordance with a
 preferred embodiment of the present invention. Decontamination system 300
 includes decontamination tank 302 which holds one or more enclosures 308.
 Each enclosure 308 may be plugged with an ultraviolet-activated plug 304,
 which either allows visible light from ultraviolet lamps contained within
 enclosures 308 to exit while blocking the ultraviolet light, or which
 absorbs ultraviolet light and generates visible light. Conductor 306 may
 extend through an ultraviolet-activated plug 304 to a lamp contained
 within an enclosure 308.
 Enclosures 308 are preferably quartz tubes, but may be formed of other
 suitable shapes and materials for holding an ultraviolet lamp. An
 enclosure 308 may contain an ultraviolet lamp that receives power through
 conductor 306. An ultraviolet lamp emits radiation into decontamination
 tank 302 that causes contaminants within contaminated media contained in
 decontamination tank 302 to break down and/or be reduced or oxidized.
 In operation, an operator may determine the operational status of the
 ultraviolet lamps contained within each enclosure 308 by observing the
 status of ultraviolet-activated plug 304. If ultraviolet-activated plug
 304 is emitting light, that indicates that the lamp contained within
 enclosure 308 is active. Alternatively, if ultraviolet-activated plug 304
 is not emitting light, that indicates that the lamp contained within that
 enclosure is not operational and may require repair or replacement. In
 response, an operator may remove ultraviolet-activated plug 304 and then
 remove the failed lamp. For example, the failed lamp may be connected to a
 conductor 306 that extends through a penetration of ultraviolet-activated
 plug 304. The failed lamp may be disconnected from conductor 306 and
 removed from enclosure 308, and the new lamp may then be inserted into the
 enclosure 308 and connected to conductor 306. The enclosure 308 is then
 sealed with ultraviolet-activated plug 304. In this manner, the
 ultraviolet lamps of decontamination system 300 may be replaced in service
 without requiring decontamination system 300 to be taken out of service.
 Also, if an enclosure 308 has catastrophically failed such that the media
 contained within decontamination tank 302 has entered the enclosure 308,
 this may be determined by an electrical continuity test using conductor
 306 (for liquid media), or through other means, such as by observing
 leakage around ultraviolet-activated plug 304 during plug removal. In that
 event, ultraviolet-activated plug 304 may be kept in place to allow
 decontamination system 300 to operate until a scheduled outage occurs and
 the liquid contained within decontamination tank 302 has been drained.
 FIG. 4 is a diagram of an injection mold 400 for manufacturing a plug in
 accordance with a preferred embodiment of the present invention. Injection
 mold 400 includes mold halves 402 and 404, respectively. Mold halves 402
 and 404 are configured to form a complete injection mold for the
 manufacture of a plug, such as, for example, plug 102 or plug 202 of FIGS.
 1 and 2, respectively. As illustrated in FIG. 4, mold halves 402 and 404
 are operable for the manufacture of plug 102 of FIG. 1. Penetration
 channel 406 of mold halves 402 and 404 allows a penetration spacer 408 to
 be inserted into the mold to allow a suitable cable penetration to be
 formed. Also or alternatively, mold halves 402 and 404 may be configured
 for no penetration, and a penetration may be formed by machining one or
 more holes axially through the plug formed by the injection molding
 process.
 In addition, mold half 404 includes injection port 410. A suitable plug
 material may be injected into injection mold 400 through injection port
 410. For example, the material may be an epoxy, a plastic, a polymer, or
 other suitable materials that are ultraviolet blocking or ultraviolet
 luminescent, or that contain ultraviolet blocking or ultraviolet
 luminescent fillers. In this manner, the operational status of an
 ultraviolet lamp contained within an enclosure be determined by an
 operator.
 In operation, mold halves 402 and 404 are placed together, either with a
 penetration spacer 408, or without penetration spacer 408 in the event
 that a penetration will be machined. A suitable material is injected
 through injection port 410, and after the material has set the mold halves
 are removed, allowing the formed plug to be further processed.
 FIG. 5 is a flow chart of a method 500 for decreasing ozone generation in a
 decontamination system in accordance with a preferred embodiment of the
 present invention. Method 500 begins at step 502, where the ultraviolet
 lamps for the decontamination system are placed into enclosures, such as a
 quartz tube assembly or rack. The method then proceeds to step 504, where
 the enclosures are sealed with an airtight plug that has been formed from
 a material that is responsive to ultraviolet radiation. For example, the
 material may be polycarbonate or other suitable materials that absorb the
 ultraviolet radiation and transmit the visible light generated by the
 ultraviolet lamps. Also or alternatively, the material may be an
 ultraviolet-luminescent material that absorbs ultraviolet light and
 generates visible light, or the material may be a polymer or other
 suitable base material that has an ultraviolet-luminescent material
 dissolved or dispersed within.
 The enclosure may be sealed, for example, by installing the plug into the
 enclosure with an o-ring seal that is configured to provide a sealing
 force, or may also or alternatively be sealed by installing the plug into
 the enclosure with a nut that is used to apply a sealing force to an
 o-ring, a gasket, or other suitable seal. After the enclosure has been
 sealed at step 504, the method proceeds to step 506.
 At step 506, a sealing force is applied to the plug if necessary. For
 example, if a nut is used to hold the plug in place and to apply a sealing
 force to the plug, then the nut may be torqued to a predetermined torque
 to apply a sealing pressure to the o-ring, gasket, or other sealing
 material. Alternatively, the plug may be threaded if the cable penetration
 through the plug is capable of allowing the plug to rotate about an axis
 without causing the cable to twist and become damaged, in which case a
 sealing torque is applied directly to the plug at step 506. The method
 then proceeds to step 508.
 At step 508, the ultraviolet lamps are connected to a power source by
 connecting the electrical penetration to a cable and power source, as
 suitable. All of the ultraviolet lamps in a decontamination or
 sterilization rack may be connected either in series or in parallel, as
 suitable, but are typically connected in parallel. The status of the plugs
 and thus the lamps is then monitored at step 510. For each plug, it is
 determined whether the plug is emitting visible light at step 512. If the
 plug is not emitting visible light, then the method proceeds to step 514
 where the ultraviolet lamp for the corresponding enclosure is replaced. If
 it is determined at step 512 that the plug is emitting light, then the
 method proceeds to step 516, where the next plug to be monitored is
 determined. The method then returns to step 512 for monitoring of
 subsequent plugs.
 In operation, method 500 may be used to monitor the status of radiation
 sources such as an ultraviolet lamps for decontamination and disinfection
 equipment without requiring the use of expensive automatic monitoring
 equipment that performs electrical measurements, or that requires
 electrical or electronic sensors. Method 500 is adapted for use in systems
 that may continue to operate with several radiation sources disabled, such
 that the radiation sources are typically replaced according to a
 predetermined maintenance schedule. Method 500 is also adapted for use
 with systems that allow the radiation sources to be changed out
 in-process, such that failed lamps may be removed from lamp enclosures and
 replaced with operational lamps without removing the system from
 operation.
 FIG. 6 is a flow chart of a method 600 for making a plug in accordance with
 the preferred embodiment of the present invention. Method 600 begins at
 step 602, where a polycarbonate rod segment is inserted into a machining
 device. For example, the machining device may be a milling machine or
 other suitable machining devices. The method then proceeds to step 604.
 At step 604, an o-ring seat or other suitable seal is machined into the
 polycarbonate rod. For example, a channel may be machined
 circumferentially around the rod with a suitable width so as to accept and
 hold an o-ring seal. The method then proceeds to step 606, where it is
 determined whether additional diametric restrictions are required. For
 example, the enclosure may include a chamfered edge such that the plug
 seats against the chamfer. Also or alternatively, threads may be machined
 onto the plug such as if a free-turning cable penetration is used so that
 the plug may be tightened without placing a torque on the cable that
 penetrates the plug. If it is determined at step 606 that these additional
 diametric restrictions are required, the method proceeds to step 608 where
 the additional diametric restrictions are machined onto the polycarbonate
 rod. The method then proceeds to step 610.
 At step 610, a cable penetration is machined into the plug. For example, a
 single cable penetration may be drilled axially through the centerline of
 the plug, two or more cable penetrations may be drilled axially through
 various locations on the plug, or other suitable cable penetrations may be
 formed. The method then proceeds to step 612, where a conductor is
 threaded through the penetration or penetrations formed at step 610. For
 example, a conductor may be threaded through a machined penetration such
 that the conductor jacket forms a seal against the penetration.
 Alternatively, a penetration assembly may be used that allows the plug to
 rotate around the conductor, such that no torque is applied to the
 conductor if the seal rotates. Other suitable configurations may also be
 used to provide the conductor through the plug to the interior of the
 enclosure.
 In operation, method 600 may be used to manufacture a plug that either
 blocks harmful radiation from an ultraviolet lamp or other radiation
 source while allowing visible light to pass through the plug, or that
 absorbs the harmful radiation and emits visible light. Method 600 may be
 automated so as to be performed without operator intervention, or may also
 or alternatively include steps that require operator action.
 FIG. 7 is a flow chart of a method 700 for manufacturing a plug in
 accordance with a preferred embodiment of the present invention. Method
 700 may be used to manufacture a plug using an injection molding process.
 Method 700 begins at step 702, where an injection mold having suitable
 plug dimensions is formed, such as from a machining process in which
 computer-assisted design drawings are used to control a machining device
 that machines the mold halves from a suitable material. The method then
 proceeds to step 704, where a conductor or spacer is placed in a
 penetration channel of the mold, if one is utilized. The mold halves or
 other pieces are then assembled at step 706.
 The method then proceeds to step 708, where ultraviolet-active material is
 injected into the mold. For example, an epoxy, plastic, polymer or other
 suitable material that is ultraviolet-luminescent or that contains
 ultraviolet-luminescent fillers may be injected through an injection port
 of the mold and is allowed to cure. Also or alternatively, the material
 used to form the plugs may be an ultraviolet-absorbing material that
 allows visible light to pass through, such as a polycarbonate material.
 Curing may take place at certain predetermined temperatures or under other
 suitable conditions. The method then proceeds to step 710, where the plug
 is removed from the mold and prepared for use, such as by sanding,
 machining, and/or finishing.
 In operation, method 700 may be used to manufacture plugs for enclosures
 that hold ultraviolet lamps for decontamination or disinfection processes.
 The lamp plugs manufactured by method 700 may require additional
 processing before they are suitable for use in an enclosure, or may be
 manufactured to be ready-to-use.
 While an embodiment of the present invention has been described in detail,
 the present invention may include embodiments different from those
 described, yet within the scope of the claims. For example, the "plug,"
 "o-ring seal," "enclosure," and "ultraviolet lamp" may be implemented in a
 manner that is functionally identical but structurally different from that
 shown herein. Such changes are contemplated as being within the scope of
 the present invention. Likewise, the present invention may be implemented
 in disinfection and decontamination systems that use air or other suitable
 gases and water or other suitable solvents. Although ultraviolet lamps
 have been described in many of the figures, any suitable radiation source
 may be used in the embodiments shown without departing from the spirit or
 the scope of the present invention. Suitable radiation active materials,
 such as those that block the transmission of the radiation source while
 allowing visible light to be transmitted, and those that absorb the
 radiated energy from the radiation source and emit visible light, may be
 used where suitable.
 While the present invention has been described with reference to a
 preferred embodiment, this description is not intended to be construed in
 a limiting sense. Various modifications and combinations of the preferred
 embodiment, as well as other embodiments of the invention, will be
 apparent to persons skilled in the art upon reference to the description.
 It is therefore intended that the appended claims not be limited to the
 described preferred embodiment and instead encompass any such
 modifications or embodiments.