Patent Description:
A flame detection system may be configured to sense or detect various attributes of a flame or an impending/burgeoning flame. The flame detection system may include an ultraviolet (UV) sensor that detects UV radiation emitted from the flame. The flame detection system outputs an alarm upon detection of UV radiation greater than a threshold. The flame detection system may erroneously output an alarm due to UV radiation from ambient light. Furthermore, current manufacturing methods of flame detection systems incorporating the UV sensing elements are fairly expensive. <CIT> discloses a light detector having spaced electrodes preset by pins or a spacer within a sealed enclosure. <CIT> discloses an ultra-thin radiation detector including a radiation detector gas chamber having at least one ultra-thin chamber window and an ultra-thin first substrate contained within the gas chamber. <CIT> discloses an ultraviolet ray sensor for operating at high temperature including a gas-filled sealed unit which encloses a photocathode having a spherically-shaped metal crystalline end and a ray collecting means for gathering and focusing incident rays on the photocathode. <CIT> discloses a flame detector for detection of the presence of a flame or spark in front of the detector comprising a UV sensitive photocathode and an anode.

According to an aspect of the invention there is provided a flame detector as recited in claim <NUM>.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, at least one of the anode and the cathode defines a plurality of perforations.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the UV sensing elements include a partially transmissive material disposed on a surface of UV transparent window.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, a second UV transparent window disposed at the second spacer end.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the UV sensing elements include a second partially transmissive material disposed on a surface of the second UV transparent window.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the recess includes a first surface that is disposed parallel to the first axis and a second surface that extends from the first surface and is disposed perpendicular to the first axis.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the second surface extends from an inner surface towards an outer surface.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, the UV transparent window includes a pair of window surfaces and a circumferential surface that extends between the pair of window surfaces.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, at least one of the pair of window surfaces of the UV transparent window engages the second surface.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, a central plate disposed within the gas space and disposed between the UV transparent window and the second UV transparent window.

According to another aspect of the invention there is provided a method of manufacturing a flame detector as recited in claim <NUM>.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, cleaning the anode and the cathode.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, heating the first joining material to a first temperature within a vacuum process chamber to join the UV transparent window to the end surface of the spacer; and heating the second joining material to a second temperature within the vacuum process chamber to join at least one of the anode and cathode of the UV sensing elements to the spacer, wherein the second temperature is different from the first temperature.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, cleaning the partially assembled flame detector within the vacuum process chamber.

The gas space within the spacer is filled with a gas composition arranged to enable a gas electron multiplier effect.

In addition to one or more of the features described above, or as an alternative to any of the foregoing embodiments, applying at least one of the first joining material and the second joining material to a second end surface of the spacer disposed opposite the end surface; disposing a second UV transparent window on at least one of the first joining material and the second joining material; and heating at least one of the first joining material and the second joining material within the vacuum process chamber to join the second UV transparent window to the second end surface of the spacer.

The present disclosure provides a compact UV flame detector capable of two-sided detection of flames through UV transparent caps or windows. The UV flame detector is made by a process that minimizes manual handling of the clean UV flame detector parts and employs a vacuum process chamber having dual heating zones that function at different temperatures. The dual heating zones facilitate the processing of the UV flame detector within a single vacuum process chamber.

Referring to <FIG>, an ultraviolet (UV) flame detector <NUM>, is shown. The UV flame detector <NUM> is arranged to receive UV light from a flame that may cause a photoelectric response within the UV flame detector <NUM> such that a fire or a flame may be detected. The UV flame detector <NUM> includes a spacer <NUM>, a UV transparent window <NUM> and a UV sensing elements <NUM>.

The spacer <NUM> is arranged as a vessel, a housing, a tube or the like that receives the UV sensing elements <NUM>. The spacer <NUM> is at least partially sealed by the UV transparent window <NUM> at a first spacer end <NUM> and is completely sealed at a second spacer end <NUM> by the UV sensing elements <NUM>. The spacer <NUM> may be made of a ceramic material, however other electrically insulating and vacuum tight are also contemplated.

The spacer <NUM> includes a spacer wall <NUM> having an inner surface <NUM> and an outer surface <NUM> that is disposed opposite the inner surface <NUM>. The inner surface <NUM> and the outer surface <NUM> each extend along a first axis <NUM> (e.g. a central longitudinal axis) between the first spacer end <NUM> and the second spacer end <NUM>.

An axial length of the spacer <NUM>, along the first axis <NUM>, may be substantially equal to a cross-sectional form (e.g. cross-sectional diameter) of the spacer <NUM>. In other embodiments, the axial length of the spacer <NUM> may be different than the cross-sectional form of the spacer <NUM>.

The inner surface <NUM> of the spacer wall <NUM> and a portion of the UV transparent window <NUM> define an internal volume or a gas space <NUM> that receives a gas mixture of composition and pressure suitable to enable signal amplification by virtue of the gas electron multiplier effect, for the UV sensing elements <NUM>. The spacer wall <NUM> circumscribes or is disposed about the gas space <NUM>.

The spacer wall <NUM> defines a first gap <NUM> and a second gap <NUM>. The first gap <NUM> is disposed proximate the first spacer end <NUM> and extends about the spacer wall <NUM>. The first gap <NUM> extends from the inner surface <NUM> towards the outer surface <NUM>. The second gap <NUM> is disposed proximate the second spacer end <NUM> and extends about the spacer wall <NUM> and the second gap <NUM> is spaced apart from the first gap <NUM>. The gaps may be openings, notches, grooves, recesses, through holes, ledges, or the like that are arranged to at least partially receive or retain a portion of the UV sensing elements <NUM> and be filled with a bonding/sealing material.

The spacer wall <NUM> defines a recess <NUM>, as shown in <FIG>. The recess <NUM> axially extends from the first spacer end <NUM> towards the second spacer end <NUM> along the first axis <NUM>. The recess <NUM> radially extends from the inner surface <NUM> towards the outer surface <NUM>.

The recess <NUM> includes a first surface <NUM> and a second surface <NUM>. The first surface <NUM> is disposed parallel to the first axis <NUM> and extends from the first spacer end <NUM> towards the second spacer end <NUM>. The first surface <NUM> may extend to the second surface <NUM>. The second surface <NUM> may be disposed generally perpendicular to the first axis <NUM>. The second surface <NUM> may extend from the first surface <NUM> towards the inner surface <NUM>.

The spacer wall <NUM> may define or include an end surface <NUM>, as shown in <FIG>, which does not fall within the scope of the appended claims. The end surface <NUM> may be a generally planar surface that is disposed at the first spacer end <NUM>. The end surface <NUM> may be the first spacer end <NUM> and may be disposed substantially transverse to first axis <NUM>.

Referring to <FIG>, and <FIG>, the UV transparent window <NUM> is disposed proximate the first spacer end <NUM> and is sealingly joined to the spacer <NUM>. The UV transparent window <NUM> may be an optical window made from UV transmissive materials such as sapphire, glass, or other UV transmissive materials.

The UV transparent window <NUM> includes a first window surface <NUM>, a second window surface <NUM>, and a side surface or a circumferential surface <NUM>. The first window surface <NUM> may be disposed opposite the second window surface <NUM>. The first window surface <NUM> and the second window surface <NUM> may form a pair of generally planar surfaces, may form a pair of generally non-planar surfaces, or may be in the form of a lens (e.g. concave or convex lens) if there is a need to focus the imaging field of view of the sensor. The circumferential surface <NUM> extends between the pair of window surfaces.

The UV transparent window <NUM> may be at least partially received within the recess <NUM>, as shown in <FIG>. The circumferential surface <NUM> may engage or may disposed on the first surface <NUM> of the recess <NUM>. At least one of the window surfaces (e.g. the first window surface <NUM> or the second window surface <NUM>) may engage or may be disposed on the second surface <NUM> of the recess <NUM>. The UV transparent window <NUM> may be joined to the recess <NUM> to at least partially seal the spacer <NUM> by a first joining material <NUM>. The first joining material <NUM> may be disposed on and between the first surface <NUM> and the second surface <NUM> of the recess <NUM> and the circumferential surface <NUM> and the second window surface <NUM> of the UV transparent window <NUM>.

The UV transparent window <NUM> may engage or be disposed on the end surface <NUM> of the spacer wall <NUM>, as shown in <FIG>. The UV transparent window <NUM> may be joined to the end surface <NUM> to at least partially seal the spacer <NUM> by a first joining material <NUM>. The first joining material <NUM> may be disposed on the end surface <NUM> of the spacer <NUM>.

A transparent cover or a second UV transparent window <NUM> is disposed opposite the UV transparent window <NUM>, as shown in <FIG>. The second UV transparent window <NUM> may have a substantially similar configuration as the UV transparent window <NUM>. The second UV transparent window <NUM> may be disposed proximate or on the second spacer end <NUM>. The second UV transparent window <NUM> may abut or extend at least partially into the spacer wall <NUM> proximate the second spacer end <NUM>. The second UV transparent window <NUM> may be joined to the spacer wall <NUM> to at least partially seal the spacer <NUM> by the first joining material <NUM> or a second joining material.

The UV sensing elements <NUM> are disposed within the gas space <NUM>. The UV sensing elements <NUM> includes an anode <NUM> and a cathode <NUM>.

The anode <NUM> is disposed proximate the UV transparent window <NUM> proximate the first spacer end <NUM>. The anode <NUM> is arranged to collect or attract emitted electrons from the cathode <NUM>. The anode <NUM> includes a perforated region or a perforated feature <NUM> defining a plurality of perforations.

The anode <NUM> extends into the first gap <NUM> of the spacer wall <NUM> and/or is joined to the spacer wall <NUM> proximate or within the second gap <NUM>, proximate the first spacer end <NUM>. The anode <NUM> may be secured within the first gap <NUM> by a second joining material <NUM>.

The perforated feature <NUM> is disposed between or spaced apart from outer edges or ends of the anode <NUM>. The perforated feature <NUM> extends towards the cathode <NUM>. The perforated feature <NUM> is arranged to permit light that enters through the UV transparent window <NUM> to pass to the cathode <NUM>.

The cathode <NUM> is disposed within the gas space <NUM> and is spaced apart from the perforated feature <NUM> of the anode <NUM> by an insulating gap or an insulating space. The cathode <NUM> is photosensitive such that the cathode <NUM> emits electrons when exposed to UV light or illuminated. A voltage difference between the anode <NUM> and the cathode <NUM> in the presence of illumination or UV light enables the UV flame detector <NUM> to detect the presence of a flame. The cathode <NUM> may be a photo cathode that includes a recessed portion or an extension <NUM>.

The cathode <NUM> extends into the second gap <NUM> of the spacer wall <NUM> and/or is joined to the spacer wall <NUM> proximate or within the second gap <NUM>, proximate the second spacer end <NUM>. The cathode <NUM> may be secured within the second gap <NUM> by the second joining material <NUM>.

The recessed portion or extension <NUM> is disposed between or spaced apart from outer edges or ends of the cathode <NUM>. The extension <NUM> extends towards the perforated feature <NUM> of the anode <NUM>.

The extension <NUM> may define a plurality of perforations, as shown in <FIG>. The perforations of the extension <NUM> of the cathode <NUM> may be offset from the perforations of the perforated feature <NUM> of the anode <NUM> such that the perforations of the extension <NUM> of the cathode <NUM> are misaligned with the perforations of the perforated feature <NUM> of the anode <NUM>. In this arrangement, light may pass through the UV transparent window <NUM> disposed proximate the first spacer end <NUM> and the light may pass through the perforated feature <NUM> of the anode <NUM> and fall on the solid surfaces of the cathode <NUM>. Furthermore, light may also pass through the second UV transparent window <NUM> disposed proximate the second spacer end <NUM> and the light may pass through the perforations of the extension <NUM> of the cathode <NUM> and fall on the solid surfaces of the anode <NUM>.

External electronics may be connected to the anode <NUM> and the cathode <NUM> that may switch the polarity (e.g. applying AC power that switches polarity with time) applied to the anode <NUM> and the cathode <NUM> to enable the sequential two-sided detection as described above. The polarity may be alternated such that the UV flame detector <NUM> may sequentially detect a flame through the UV transparent window <NUM> for a first time period and then detect a flame through the second UV transparent window <NUM> for a second time period.

The examples shown in <FIG>, <FIG>, <FIG> and described in the following are for illustrative purposes only and do not fall within the scope of the appended claims. A partially transmissive surface or a partially transmissive material <NUM> may be disposed on or proximate the UV transparent window <NUM>, as shown in <FIG>. The partially transmissive material may be disposed on or proximate at least one of the first window surface <NUM> and/or the second window surface <NUM>. The partially transmissive material may be a metal in a grid or other pattern that allows light to pass to the UV sensing elements <NUM>. The partially transmissive material may function in a similar manner as an anode, eliminating the need for a traditional anode.

A partially transmissive surface or a partially transmissive material <NUM> may be disposed on or proximate the second UV transparent window <NUM>, as shown in <FIG>. The partially transmissive material may be a metal in a grid or other pattern that allows light to pass to the UV sensing elements <NUM>. The metal applied to the second UV transparent window <NUM> may be of a suitable work function to provide sensitivity to selected or specific wavelengths, such as nickel. The partially transmissive material may function in a similar manner as a cathode, eliminating the need for a traditional cathode.

A partially transmissive material <NUM> may be disposed on a surface of the UV transparent window <NUM> and a second partially transmissive material <NUM> may be disposed on a surface of the second UV transparent window <NUM>, as shown in <FIG>. The partially transmissive material <NUM> may replace the anode <NUM> and the second partially transmissive material <NUM> may replace the cathode <NUM>. The partially transmissive material <NUM> may be patterned with holes, gaps, or openings that are offset from holes, gaps, or openings that are patterned within the second partially transmissive material <NUM>. This arrangement provides two-sided sensitivity of the UV flame detector <NUM>, enabling opposing ends of the UV flame detector <NUM> to detect the presence of a flame and also minimizes the overall size of the UV flame detector <NUM>.

The replacement or substitution of at least one of the anode <NUM> and/or the cathode <NUM> of the UV sensing elements <NUM> with partially transmissive materials <NUM>, <NUM>, as shown in <FIG>, may aid in reducing the overall size of the UV flame detector <NUM> and simplify the arrangement of the UV flame detector. These arrangements may also ease fabrication of the UV flame detector <NUM>.

The UV flame detector <NUM> may be arranged in an array with other UV flame detectors. A first plurality of UV flame detectors may be arranged within or on a first member having a first shape. A second plurality of UV flame detectors be arranged within or on a second member having a second shape. The second member may be joined to the first member and oriented relative to the first member such that a <NUM>-D or multiple dimension array of UV flame detectors. The first shape and the second shape may have a generally planar, arcuate, or other shape.

Referring to <FIG>, the UV flame detector <NUM> may be arranged as a double ended UV tube. A first patterned metal anode <NUM> or partially transparent elements or films may be disposed on a surface of the UV transparent window <NUM>, as shown in <FIG>, and a second patterned metal anode <NUM> may be disposed on a surface of the second UV transparent window <NUM> or partially transparent elements or films, as shown in <FIG>. The UV transparent window <NUM> having the first patterned metal anode <NUM> is disposed at or affixed to the first spacer end <NUM> and the second UV transparent window <NUM> having the second patterned metal anode <NUM> is disposed at or affixed to the second spacer end <NUM>.

A central plate <NUM> extends into the gas space <NUM> and is disposed between the UV transparent window <NUM> having the first patterned metal anode <NUM> and the second UV transparent window <NUM> having the second patterned metal anode <NUM>. The central plate <NUM> serves as a cathode (e.g. photo-responsive element) for each side of the UV tube, e.g. the first spacer end <NUM> and the second spacer end <NUM>. The central plate <NUM> may be fabricated with perforations or other features outside of the photo-active area to allow both sides of the double ended UV tube to share the same fill gas. In at least one embodiment, the gas space <NUM> may be separated into two distinct and separate gas spaces by the central plate <NUM>, such that a region between the central plate <NUM> and the first spacer end <NUM> defines a first UV tube <NUM> and another region between the central plate <NUM> and the second spacer end <NUM> defines a second UV tube <NUM>. The first UV tube <NUM> is connected to separate circuitry from the second UV tube <NUM> to register the signals from each other by either multiplexing or dedicated circuitry.

The arrangement of the double ended UV tube of <FIG> eliminates the need to align offset holes in anode/cathode pairs to achieve double-ended sensitivity, thereby simplifying fabrication of the UV flame detector <NUM>. The arrangement of the double ended UV tube of <FIG> eliminates the need for alternating polarity voltage for operation because the first patterned metal anode <NUM> and the second patterned metal anode <NUM> may be at the same potential, with the central plate <NUM> or cathode at the opposite polarity.

The UV flame detector <NUM> may be more compact as compared to previous flame detector designs as well as having greater resistance to physical shock and vibration due to the construction and manufacturing process as will be described below.

The manufacturing process with which the UV flame detector <NUM> may be manufactured includes providing the spacer <NUM>, the UV transparent window <NUM>, the anode <NUM>, and the cathode <NUM>.

The first joining material <NUM> may be applied to a surface of the UV transparent window <NUM> or may be applied to at least one of the recess <NUM> and/or the end surface <NUM> of the spacer wall <NUM>. The first joining material <NUM> may be a solder or other joining material having a first melting point.

The second joining material <NUM> may be applied to the first spacer end <NUM> and the second spacer end <NUM>. The second joining material <NUM> may be applied to the first gap <NUM> and the second gap <NUM> to seal the gaps. The second joining material <NUM> may be a solder or other joining material having a second melting point. The second melting point of the second joining material <NUM> may be greater than the first melting point of the first joining material <NUM>. In at least one embodiment, the second melting point of the second joining material <NUM> may be substantially equal to the first melting point of the first joining material <NUM> such that the first joining material <NUM> is the same as the second joining material <NUM>.

The spacer <NUM>, the UV transparent window <NUM>, the anode <NUM>, and the cathode <NUM> may be cleaned using various cleaning processes, as known to one of ordinary skill in the art. In at least one embodiment, the anode <NUM> and/or the cathode <NUM> may be further cleaned to provide a clean, smooth, and oxide free surfaces.

The UV transparent window <NUM> may be disposed proximate but spaced apart from the spacer <NUM> by a fixture, such that the UV transparent window <NUM> is disposed proximate an end surface of the spacer <NUM>. The anode <NUM> and the cathode <NUM> of the UV sensing elements <NUM> may be disposed within the spacer <NUM>, having their respective ends extend into but spaced apart from their respective gaps of the spacer wall <NUM> by the fixture.

A vacuum process chamber having heaters may be preheated to a predetermined temperature and may also have a vacuum applied prior to the partially assembled UV flame detector <NUM> being disposed within the vacuum chamber. The fixture that spaces the various components of the partially assembled UV flame detector <NUM> apart from each other may be provided with the vacuum process chamber.

The partially assembled UV flame detector <NUM>, comprising of the UV transparent window <NUM>, the spacer <NUM>, the anode <NUM>, and the cathode <NUM> may be disposed within the vacuum process chamber. The partially assembled UV flame detector <NUM> may be essentially an open-ended tube at this point in the manufacturing process.

The vacuum process chamber may be provided with dual heating zones that function at different temperatures to enable the processing of the UV flame detector <NUM> within a single process chamber. In such an arrangement, the vacuum process chamber includes a first heater disposed within or defining a first heat zone and a second heater disposed within or defining a second heat zone. The first and second heaters may be arranged as radiant heaters. In at least one embodiment, a single heater defining a single heat zone may be provided. The single heater may be capable of operating at two different temperatures such that a first temperature may be applied to a first portion of the partially assembled UV flame detector <NUM> and a second temperature to a second portion of the partially assembled UV flame detector <NUM> that is disposed opposite the first portion.

A heat shield may be disposed between the first heat zone and the second heat zone to inhibit or restrict heat transfer between the first heat zone and the second heat zone. The first spacer end <NUM> upon which the UV transparent window <NUM> may be disposed, may extend into or may be disposed within the first heat zone. The first heater is provided to heat the first joining material <NUM> to a first temperature, such as proximate the first melting point. The second spacer end <NUM> may extend into or may be disposed within the second heat zone. The second heater is provided to heat the second joining material <NUM> to a second temperature, such as proximate the second melting point. The vacuum process chamber may substantially simultaneously apply a vacuum and apply heat to the partially assembled UV flame detector <NUM> to melt the joining materials. Alternatively, the vacuum and the heating may be applied serially.

The UV transparent window <NUM> may be joined to the spacer <NUM> by the heating/melting of the first joining material <NUM> by the first heater to seal the spacer <NUM>. In at least one embodiment, the UV transparent window <NUM> may be brought into contact with at least a portion of the anode <NUM> and may ultimately be joined to at least a portion of the anode <NUM>. The UV transparent window <NUM> may be joined to the spacer <NUM> subsequent to the UV sensing elements <NUM> being joined to the spacer <NUM>.

The anode <NUM> and the cathode <NUM> may be joined to the spacer <NUM> by the melting of the second joining material <NUM> by the second heater.

The partially assembled UV flame detector <NUM> may be cleaned within the vacuum process chamber using a method that may remove any remaining contaminants. At least a portion of any remaining contaminants may be pumped or removed from the vacuum process chamber to achieve a predetermined acceptable level of cleanliness or predetermined acceptable level of contaminants. The initial and the subsequent cleaning of the UV flame detector within the vacuum process chamber limits or inhibits the formation of deposits (or gas phase contaminants) should the gas composition become excited during detection, limiting the possibility of false alarms or erroneous detection of flames.

The gas space <NUM> according to all embodiments is filled with the gas composition. The gas composition is arranged to enable a gas electron multiplier effect. The gas space <NUM> may be filled with the gas composition through a port or a tube.

At least one of the first joining material <NUM> and the second joining material <NUM> may be applied to a second end surface of the spacer <NUM> that is disposed opposite the end surface of the spacer <NUM>. The second UV transparent window <NUM> may be joined to the second end surface of the spacer <NUM> by the melting/heating of east one of the first joining material <NUM> and the second joining material <NUM> to seal the spacer <NUM>. In at least one embodiment, the second UV transparent window <NUM> may be brought into contact with at least a portion of the cathode <NUM> and may ultimately be joined to at least a portion of the cathode <NUM>. The second UV transparent window <NUM> may be joined to the spacer <NUM> subsequent to the UV sensing elements <NUM> being joined to the spacer <NUM>.

The assembled UV flame detector <NUM> may be cooled within the vacuum process chamber to a predetermined temperature to enable or facilitate the handling of the UV flame detector <NUM>. Upon achieving the predetermined temperature, the assembled UV flame detector <NUM> may be removed from the vacuum process chamber.

Claim 1:
A flame detector, comprising:
a spacer (<NUM>) having a spacer wall (<NUM>) disposed about a gas space (<NUM>), the spacer wall (<NUM>) extending along a first axis (<NUM>) between a first spacer end (<NUM>) and a second spacer end (<NUM>), the spacer wall (<NUM>) defining a recess (<NUM>) that extends from the first spacer end (<NUM>) towards the second spacer end (<NUM>);
a UV transparent window (<NUM>) disposed within the recess (<NUM>); and
a UV sensing elements (<NUM>) disposed within the gas space (<NUM>);
wherein the UV sensing elements (<NUM>) includes:
an anode (<NUM>) disposed within the gas space (<NUM>) and extending into a first gap (<NUM>) defined by the spacer wall (<NUM>);
a cathode (<NUM>) disposed within the gas space (<NUM>) and spaced apart from the anode (<NUM>), the cathode (<NUM>) extends into a second gap (<NUM>) defined by the spacer wall (<NUM>); and
a gas mixture within the gas space (<NUM>), the gas mixture being arranged to enable a gas electron multiplier effect.