IMPROVED LUMINOUS SIGN

Abstract: A luminous sign (10) comprising three sandwiched plates: a front transparent legend plate (12) incorporating a le­ gend (12a), a center feedthrough plate (14) having a set of termination bores (14a) and crossover bores (14b), and a back crossover cavity plate (16) having a first and second power/gas input bore (16b) (16c) and a crossover cavity (16a) across each set of crossover bores (14b). When all three plates are aligned and hermetically bonded a continuous gas passage is provided through the first power/gas input bore (16b), termination bore (14a), legend (12a), crossover bore (14b), through the crossover cavity (16a), a crossover bore (14b) and again through the legend (12a). The gas path continues through sub­ sequent passages terminating at the second power/gas input bore (16c). Into the power/gas input bores (16b) (16c) is her­ metically inserted a tubulated electrode (18) and a non-tubulated electrode respectively. When neon gas is captively insert­ ed into the tubulated electrode (18) and electrical power is applied to the electrodes, the gaz ionizes causing the legend (12a) to glow.

Description: TECHNICAL FIELD The invention pertains to the general field of luminous signs employing an ionized gas to illuminate a legend and more particularly to an improved luminous sign constructed of three sandwiched plates where the first plate incorporates the legend and the second and third plates combine to provide a continuous path for the legend illuminating gas. BACKGROUND ART Luminous signs employing a gaseous discharge legend and the methods for making these signs have been disclosed in several patents. In general, these signs are made by using two or three confronting plates where in one or two of the plates is formed a groove or cavity corresponding to the desired legend. The cavity is contiguously attached to a gas entry port incorporating a set of electrodes. In the manufacturing process the cavity is evacuated and a quantity of gas, such as neon, is inserted under pressure and temperature into the cavity through the gas entry port which is then hermetically sealed. The partially pressurized gas is then ionized by applying a voltage across the electrode set. The ionized gas, in turn, causes the legend to illuminate. The basic problems associated with manufacturing these luminous signs lies in the method used to insulate the crossover point between two overlapping segments of a legend such as in the letter "X" or between any two letters. This problem and the solution proposed by prior disclosure is discussed in the prior art section below. A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however the following United States patents were considered related: PATENT NO. INVENTOR ISSUED 2,852,877 Goebel, et al 23 September 1958 2,158,968 Moffat 16 May 1939 1,937,957 Hotchner 5 December 1933 1,825,399 Hotchner 29 September 1931 The Goebel patent discloses two embodiments for making a luminous sign. The first consists of a transparent panel and an opaque backing panel. A groove is cut into the confronting face of the transparent panel to form the letters. The groove extends continuously from one end of the plate to the other with a tube inserted in each end into which a gas, such as neon, is introduced to the groove. The spaces between the letters are made non-luminous by inserting an opaque channel shaped shield. In the second Goebel embodiment, a transparent plate confronts an opaque plate which then confronts a second transparent plate. A groove corresponding to the legend is formed on each plate. The crossover is accomplished by etching or grinding a precision recess into one of the plates at the crossover point. A corresponding precise fitting glass block with a connecting groove is then inserted into the recess where the block acts as an insulator between the two intersecting channels. Due to the precision required between the recess and block, it is extremely difficult and costly to create a good seal. In complex legends hundreds of crossover points may exist requiring hundreds of precisions recesses and blocks adding further to the cost. The placement of the precision block into its recess can also cause problems when applying and curing adhesives as differences in the coefficients of thermal expansion of the adhesives and glass will cause stresses or cracks when the sign is heated to 450 degrees Farenheit, the temperature considered to be the absolute minimum temperature to decontaminate the neon filled channels to effect optimum illumination. The failure of only one out of number of block/recess in locations becomes evident only after final fabrication and bonding of the lamination. Thus, one small hairline leak in the seal can render the entire sign useless. Additionally, this technique results in the reduction of the cross-sectional area of the gas filled channel as it passes through the blocks, thus causing the luminous intensity and heat output of the gas to increase significantly. The Moffat patent discloses a method for constructing an incandescent gas sign in which three plates of plastic or glass are hermetically attached in a sandwiched fashion. The front and back plates are flat and confront a middle plate that has a gas containing channel, representing a legend, cut therethrough. A gas receiving opening with an electrode is located on one end of the channel and another electrode is located on the other end of the channel. The electrodes are used to ignite and illuminate the gas. The first listed Hotchner patent discloses a luminous sign constructed of a light transmitting plate having a light source secured around the perimeter of the plate. The faces of the plate are covered with a reflective film. This film confines the transmitted light within the plate except in those areas where the film has been removed to simulate a legend. Thus, the legend becomes luminous to the eye. The second listed Hotchner patent discloses a method for fabricating a flat tubeless ionization conductor device. The device comprises two glass plates having legend channels etched in an offset such that the channel may crossover itself without creating a short circuit. This is accomplished by etching each channel with an offset portion that is undercut when formed leaving an overhanging lip extending from the edge over the groove. The opposing lip separates the two superposed portions of the discharge passage at each return bend in the passages. An alternative crossover method is to burrow a tunnel below the surface of the plate such that a bridge of glass remains over the tunnel which may then pass underneath another channel in the legend. Although both methods are possible, they are impractical as they require precision etching which would be very impractical and time consuming if a large number of crossover points were necessary. Further, although it is possible to etch a short tunnel into a glass plate, it is practically impossible to etch a curved tunnel or one of longer length as would be required for complex legends. GB-A-400 646 relates to display signs which are illuminated. The display sign has a front glass sheet, a rear sheet (22) and an interposed layer (23), including grooves, some interrupted, to define gas chambers to outline characters. BE-A-493 924 shows three sheets (1), (3) and (5) also having grooves therein so that when the sheets are superimposed a character will be formed. Chambers are defined by the grooves. DISCLOSURE OF THE INVENTION According to one aspect of the invention there is provided a luminous sign comprising: a front transparent legend plate having a legend consisting of a legend cavity that is formed in the back of the plate where the legend has a beginning end and an ending and the legend is interrupted at legend crossover intersections; a center feedthrough plate located behind the front transparent legend plate; a back plate located behind the center feed through plate, the back plate having a first power/gas input bore and a second power/gas input bore; means to hermetically bond all of the plates, in the order indicated; means to insert and hermetically encapsulate within the confines of the encapsulated legend cavities an optimum quantity of an ionizable gas; and means to activate the ionizable gas such that the gas causes a luminous radiation across the legend characterized in that; the center feedthrough plate has a termination bore therethrough in alignment with the beginning end and the ending end of the legend and the crossover bore in alignment with each legend crossover point of every crossover intersection; the back plate has a crossover cavity on its topside that extends over the area encompassing each of the legend crossover intersections on the front transparent legend plate and across the respective crossover bore on the center feedthrough plate; each input bore of the back plate is in concentric alignment with each of the respective termination bores on the center feedthrough plate; means is provided to align all three of the plates in the order indicated; and the means to hermetically bond all three of the plates, is accomplished by (a) selectively applying a temperature-sensitive adhesive to the contacting surface on each of the plates, (b) aligning the plates, (c) compressing the plates by a compression means, and (d) allowing the plates to cure under compression and temperature. According to another aspect of the invention there is provided a luminous sign comprising: a front transparent legend plate having a legend consisting of a legend cavity that is formed in the back of the plate where the legend has a beginning end and an ending end and the legend is interrupted at legend crossover intersections, a center plate located behind the front transparent legend plate, a back feedthrough plate located behind the center plate, the back feedthrough plate having a first power/gas input bore and a second power/gas input bore, means to hermetically bond all of the plates in the order indicated, means to insert a and hermetically encapsulate within the confines of the encapsulated legend cavities and optimum quantity of an ionizable gas, and means to activate the ionizable gas such that the gas causes a luminous radiation across the legend characterized in that: the center plate has a crossover cavity on its backside that extends over the area encompassing each of the legend crossover intersections with each crossover cavity having two crossover bores where each of the bores is located within the cavity at each end and where the crossover bores extend upwardly interfacing with the ends of the applicable legend crossover point, and with the center plate also having termination bores in alignment with the beginning and ending ends of the legend; each input bore of the back feedthrough plate is in concentric alignment with each of the respective termination bores on the center plate; means is provided to align all three plates in the order indicated; and the means to hermetically bond all three of the plates is accomplished by (a) selectively applying a temperature-sensitive adhesive to the contacting surface on each of the plates, (b) aligning the plates, (c) compressing the plates by a compression means, and (d) allowing the plates to cure under compression. The inherent design and manufacturing methodology of the improved luminous sign allows a variety of simple to complex legends to be illuminated at maximum efficiency. The invention also lends itself to allowing many color combinations to be applied to the legend and/or legend background. The invention arose out of the need for an improved method to manufacture neon signs and legends. Current methods require the bending of glass tubes into complex shapes and legends. Problems arise due to the lack of skilled craftsmen, high labor costs, lack of manufacturing economies due to the unautomated nature of the bending process, limited creative potential, and high maintenance costs due to fragility. These methods of manufacturing neon signs have virtually remained unchanged since 1923. Although there exists prior art in this area, the previous patents covering this art possess inherent problems. From a manufacturing point of view, prior art designs are physically impractical, difficult to produce, are not cost effective, and are aesthetically limited. Most of these problems arise out of the methods used to insulate crossover points in the legend. Unless crossover points, such as in the letter "X", are not insulated, a short circuit will occur and render the legend useless or severely diminished. The instant invention not only updates the manufacturing technology, but also eliminates most, if not all, of the problems associated with the manufacturing methodology presently in use. Thus, it is the primary object of the invention to manufacture neon and other luminous gas signs where a legend is made by forming a legend cavity into a front transparent plate, insulating the legend crossover points, by means of a center feed-through plate located between the front plate and a back crossover cavity plate that incorporates the legend crossover cavities. Another object of the invention is to facilitate the creation of complex legend designs. This feat is now possible and practical because of the inventive crossover insulation method. Another object is to simplify the manufacturing process. Since only simple cavity forming and glass drilling techniques are required, a multiplicity of crossover points may be made to several stacked plates simultaneously using currently available automated machinery. Another object is to produce a sign that lends itself in terms of practicality and ease to the use of many color producing chemicals and/or color coatings on both the legend and/or the legend background. In addition to the above, it is also an object of the invention to produce a luminous sign that: o is not size limited, o has a higher yield rate than existing designs- thus, further increasing its cost effectiveness, o allows flexibility in mounting by allowing the electrodes to be positioned in the side or back, and o that is reliable and maintenance free. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of the completed luminous sign applicable to both the first and second embodiments. FIGURE 2 is a cross-sectional side view of the completed luminous sign in the preferred embodiment. FIGURE 3 is a plan view of the upper side of the front transparent legend plate as used in both the preferred and second embodiments. FIGURE 4 is a plan view of the center feedthrough plate of the preferred embodiment. FIGURE 5 is a plan view of the upper side of the back crossover cavity plate of the preferred embodiment. FIGURE 6 is a plan view of the backside of FIGURE 3. FIGURE 7 is a cross-sectional side view of the completed luminous sign in the second embodiment. FIGURE 8 is a plan view of the upperside of the center crossover cavity/bore plate of the second embodiment. FIGURE 9 is a plan view of the back feedthrough plate of the second embodiment. FIGURE 10 is a cross-sectional side view of a typical tubulated electrode. FIGURE 11 is a cross-sectional side view of a typical non-tubulated electrode. FIGURE 12 is a representative block diagram of a power source. BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the inventive improved luminous sign 10, is presented in terms of a preferred embodiment, a second embodiment and modifications that are applicable to both embodiments. In addition to the structural disclosure, there is also disclosed a process for constructing the sign. The preferred embodiment of the sign 10, as shown in FIGURES 1-6, is comprised of three major elements: a front transparent legend plate 12, a center feedthrough plate 14, a back crossover cavity plate 16, a tubulated electrode 18 and a non-tubulated electrode 20. To complete the sign's utility, an external power source 30 is also required. The front transparent plate 12, as shown in FIGURE 2 in cross section and in FIGURES 3 and 6 in a front and back views respectively, functions as the frontal plate from where the selected legend is viewed. The plate may be constructed of either plate glass or plastic. The legend 12a, as shown in FIGURES 1 and 3, consists of a legend cavity that is formed from the backside of the plate 12. The cavity is formed by a cavity producing means which includes an etching process, sandblasting, grinding, a laser beam or any other cavity producing methods. In addition to the above, the legend cavity may also be formed by molding or vacuum forming the front transparent legend plate over a mold incorporating the legend. This method is well known in the art and therefore is not described or shown in the drawings. Each segment of the legend must terminate at a legend crossover intersection 12b. For example, in the legend depicted in FIGURES 1 and 3, there are two crossover intersections 12b where each intersection includes two crossover points 12c. The center feedthrough plate 14, as shown in cross section in FIGURE 2 and in a plan view in FIGURE 4, provides the bores that allow a continuous (uninterrupted) gas flow to occur from the legend beginning end 12d, through each of the crossover intersections 12b and to the legend ending end 12e. This plate is sandwiched between the front transparent plate 12 and the back crossover cavity plate 16 that is described infra. The plate 14 has a termination bore 14a therethrough in alignment with the legend beginning end 12d and the legend ending end 12e. There is also a crossover bore 14b that is in alignment with each legend crossover point 12c of every legend crossover intersection 12b. The final plate necessary to complete the first embodiment of the luminous sign 10 is the back crossover cavity plate 16 shown in cross section in FIGURE 2 and in an upper side plan view in FIGURE 5. This plate includes the input and output connections to the power source and includes on its top side the crossover cavities 16a that function with the crossover bores 14b to maintain gas continuity between the legend crossover intersections 12b. Each crossover cavity extends over the area encompassing each of the legend crossover intersections 12b located on the front transparent legend plate 12 and across the respective crossover bores 14b located on the center feedthrough plate 14. The back crossover cavity plate 16 also has a power/gas input bore 16b, 16c in concentric alignment with each of the respective termination bores 14a located on the center feedthrough plate 14. The second embodiment of the sign 10 is shown in FIGURES 1, 3, 6, 7, 8 and 9. This embodiment is also comprised of three major elements: a front transparent legend plate 12, a center crossover cavity/bore plate 24, a back feedthrough plate 26, a tubulated electrode 18, and a non-tubulated electrode 20. As with the first embodiment an external power source 30 is also needed. The front transparent legend plate 12 is dimensionally and functionally identical to that of the preferred embodiment, therefore no further description is required. The center crossover cavity/bore plate 24, shown in cross section in FIGURE 7 and in an upperside plan view in FIGURE 8, provides the bores and cavities that allow an uninterrupted gas flow from the legend beginning end 12d through each of the crossover intersections 12b, and to the legend ending end 12e. This plate is sandwiched between the front transparent legend plate 12 and the back feedthrough plate 26 described infra. The plate 24 has a termination bore 24a therethrough in alignment with the legend beginning end 12d and the legend ending end 12e. The plate also includes the crossover cavities 24b that are formed into its bottom side. The crossover cavities extend over the area encompassing each of the legend crossover intersections 12b located on the front transparent legend plate 12. Each crossover cavity 24b also has two crossover bores 24c where each bore, as best shown in FIGURE 7, is located within the cavity 24b at each end. The bores 24c extend upwardly and interface with the ends of the applicable legend crossover point 12c. The final plate necessary to complete the second embodiment of the luminous sign 10 is the back feed-through plate 26 shown in cross section in FIGURE 7 and in a plan view in FIGURE 9. This plate provides the input and output connection to the power source 30. The plate 26 is the least complex of all the other plates in that it only includes a set of power input bores 26a, 26b Each of the bores 26a, 26b are in concentric alignment with each of the respective termination bores 24a located on the center crossover cavity/bore plate 24. In the discussion that follows, each of the refinements, procedures and manufacturing steps described are applicable to both the first and second embodiment of the luminous sign 10. To further enchance the aesthetic qualities of the luminous sign, an opaque coating 12f of various legend contrasting colors may be applied to the legend back-ground area on the backside of the front transparent legend plate 12 as depicted in FIGURE 2. The coating 12f is preferably applied prior to forming the legend 12a. Thus, when the legend is formed, the coating is dissolved from the legend permitting light to be transmitted only through the legend 12a. To compliment the colored legend background the legend 12a may also be coated on its backside with a light transmissible, background contrasting coating or preferably with a color selectable phosphorescent chemical coating 12g as depicted in FIGURE 2. As a further aesthetic refinement a plurality of different phosphorescent chemicals may be applied to the legend surface at selected intervals. In this manner, the legend 12a will radiate in a plurality of colors. By combining a specific phosphorescent chemical with a specific gas,various color combinations and derivatives may be produced as shown in TABLE I. CHEMICAL GAS COLOR Manganese and lead activated Calcium MetaSilicate (CaSiO 3 :Mn:Pb) Argon Pink Neon Red Lead activated Calcium Tungstate (CaWO 4 :Pb) Argon Blue Neon Pink Zinc Orthosilicate:Manganese (ZnSiO 4 :Mn) Argon Green Neon Gold Yttrium Oxide:Europium (Y 2 O 3 :Eu) Argon Red By blending the above chemicals with each other or with other available phosphorescent chemicals, an even greater variety of colors may be produced. In applying the phosphorescent chemical coating 12g, it is important to avoid applications which are too thick as the chemical itself can block the passage of light from the ionized gas. Thicknesses ranging between .0014 to .0018 inches (35 to 40 microns) are considered best for maximum light emission. To construct the luminous sign 10 several steps such as plate alignment, hermetic bonding, and gas insertion and encapsulation are required. Each of these manufacturing steps are next described and are applicable to the design as disclosed or to more complex designs where the legend is more complex and may be designed with several independent gas passages employing different gases and several electrodes. The alignment of the plates 12, 14, 16 or 12, 24 26 may be simply accomplished by accurately cutting two adjacent edges in each panel that serve as registration edges. The angular cut must be identical and at the same location for all three plates. Another method that may be employed is to affix to each plate in at least three corners a registration mark, such as a dot or cross. Duplicate copies of the legend are then attached to each of three plates such that the distance on each plate of any point on the legend to the registration edges or registration mark is identical. Thus, when the plates are stacked, so that the registration marks are aligned or the registration edges are flush with each other, the legend image will be automatically aligned within each plate. After the alignment is verified, the required bores and cavities are formed and the plates are hermetically bonded. The hermetic bonding process is generally accomplished by using high temperature-sensitive adhesives 32 such as epoxies or silica containing sealants. The type of adhesive used and the temperature needed depends on whether the plates are glass or plastic. Typically, for glass plates, the epoxies required for this purpose cure at temperatures between 200° to 350°F (93° to 177°C) over a curing period of from 2 to 16 hours depending on the epoxy used. In addition to the heat, the plates must be cured under a compressive force to assure hermeticity. The force required is between 6 to 30 pounds per square inch (0.42 Kg/Cm 2 to 2.1 Kg/Cm 2 ) depending on the viscosity of the epoxy or sealant being used. The adhesive is generally applied over the entire surface of one of the contiguous plates or it may be applied selectively on one of the contiguous plates around the outside surface circumference of each of the bores 12a, 14b and 16b, 16c and around the outside perimeter of the legend 12a and crossover cavity 16a. The importance in either method used is to maintain hermeticity between the bores, cavities and inside plate perimeter. An additional bonding process that may be employed is to apply the selected adhesive to only the inside perimeter surface of the plates. When using this method it is especially critical to apply sufficient pressure to cause the plates to achieve a tight maximum surface contact. The use of this method does pose a problem; if the plate(s) has surface inconsistencies, the path of the gas may follow these inconsistencies, due to the lower resistance offered, and a short circuit may result. To reduce or eliminate the occurrence of short circuit(s), a very thin gasket 36 of insulation material may be placed on the top and bottom surface of the center plate 14, 24 as shown in FIGURE 7. The insulation material may be composed of a separate fine glass cloth that is laid on the plates or fine glass fibers or powder may be sprayed or deposited onto the plates by a deposition means. The important requirements of the material used is that it withstand the high compression and temperatures and that it outgas during the heating process to prevent contamination of the legend passages. By using this insulative method, the edges of the bores and cavities are better insulated to assure the required hermeticity. In practice the insulative material may be placed on the plates prior to having the required bores or cavities on the plates drilled or sandblasted. Thus, when such drilling or sandblasting occurs the insulative material from the bores or channels is automatically removed. A tubulated electrode 18, as shown in FIGURES 2 and 7, is hermetically inserted into the first power/gas input bore 16b, 26a and a non-tubulated electrode 20 is hermetically inserted into the second power/gas input bore 16c, 26b. The electrodes 18, 20 have a diameter that allows a tight fit when inserted into the respective power/gas input bores. Thus, a hermetic seal 16d is easily accomplished by applying a fillet of epoxy or sealant around the circumference of the interface. The seal is then cured by using a conventional heating process. The tubulated electrode 18, as shown in FIGURE 10, is comprised of a primary glass tube 18a having within this tube a hermetically contained metallic electrode shell 18b connected to a set of electrical lead-in wires 18d that extend outside the glass tube 18a. Hermetically attached to the end of the primary glass tube 18a is a gas input tube 18c that provides a passage through the electrodes 18 into the legend passage way. The non-tubulated electrode 20, as shown in FIGURE 11, has no gas input tube and is only comprised of a primary glass tube 20a having hermetically encapsulated therein an electrode shell 20b having an electrical lead-in wire extending out from the end of the glass tube 20a. If a tubulated electrode 18 is not used, that is, the gas input is separate from the electrical lead-in wire, then the gas is simply inserted through a small diameter glass gas tube (not shown) that is hermetically inserted into the legend gas passage way. After the tubulated electrode 18 and non-tubulated electrode are hermetically attached the structure of the luminous sign 10 is complete. At this point, the ionizable gas may be introduced into the gas input tube 18c of the tubulated electrode 18. The gas input is commenced after the sign's temperature has been elevated to at least 450° F (232° C) while under a partial vacuum. If the gas is not inserted and a vacuum maintained while the plates are being cooled from the lamination and electrode insertion process, it will be necessary to reheat and re-evacuate the structure before gas is introduced. A vacuum is accomplished by connecting a vacuum pump (not shown) to the gas input tube 18c of the tubulated electrode or the optimal glass gas tube. The connection to the gas input tubes are not made directly from the vacuum pump but rather from the pump to a control manifold (not shown) then from the manifold to the gas input tubes. The manifold, which is of a conventional type used in traditional neon shops, is comprised of glass tubes and vacuum tight stopcocks. When a vacuum pressure of approximately 15 microns is reached, the pump is isolated by means of a stopcock. The vacuum is applied at a temperature between 450 o F and 500 o F (232 o and 260 o C). The temperature should not drop below 450 o F (232 o C) because at these lower temperatures organic substances will not be drawn off by the partial vacuum and the structure will be contaminated. A contaminated structure will cause the neon not to glow or if it does glow the use life of the luminous sign 10 will be shortened. The vacuum is maintained until the structure is cooled to 150° F (66° C) or less at which time the neon gas or argon is introduced into the gas input tube 18c by opening another stopcock on the manifold that is connected to the source of neon or argon gas. When the appropriate gas pressure is reached, as shown in TABLE II, the glass tube 18a of the tubulated electrode 18 is heated to a molten state causing the partial pressure within to draw the molten tube walls inward creating a hermetic seal. The completed luminous sign 10 is then removed from the manifold. The gas pressure of the gas introduced into the structure is dependent on the average cross sectional area of the bores and cavities within the plates 12, 14, 16 or 12, 24, 26. Assuming that the cross section is equal to that of a tube of a given diameter, then the pressures necessary are given in TABLE II. Tube Diameter (Millimeters) Cross Section (Square Millimeters) Gas Pressures (Millimeters Mercury) 25 491 6 22 380 7 20 314 7.5 18 254 8 15 177 9 14 154 10 13 133 10 12 113 11 11 95 12 10 78 13 9 64 15 8 50 16 7 38 16.5 6 28 17.5 5 20 18.5 4 12.5 19.5 3 7 20.5 2 3 21.5 The above pressures are for normal room temperature conditions. If the temperature is lower, the listed pressures may vary by several millimeters or up to 20 percent higher. If the temperature at which the gas is introduced is higher due to previous heating, an appropriate adjustment must be made in accordance to Boyle's Law covering pressure verus temperature. To complete the utility of the luminous sign 10 a power source 30 is connected across the electrical lead-in wire 18d and 20c located on the tubulated electrode 18 and non-tubulated electrode 20 respectively. The power source 30 is preferably an a-c power supply operating at 60Hz and rated to supply the required voltage and current to ionize the gas within the sign 10. However, a d-c power supply as well as high frequency power supplies may also be employed. Although the invention has been described in complete detail and pictorially shown in the accompanying drawings, it is not to be limited to such details, since many changes and modifications may be made to the invention without departing from the spirit and scope thereof. For example, a reservoir cavity 25 may be created as shown on the center channel/bore plate 24 of FIGURE 8. This cavity is not part of the legend circuit and may be located anywhere on the plate 24 as long as the cavity is not over any portion of the etched legend 12a. The cavity is connected, in this example, into the crossover channel 24b by means of a narrow feeder channel 25a as also shown in FIGURE 8. The reservoir cavity 25 serves to extend the operating life of the luminous sign by providing a reservoir of gas to replenish the gas that is depleted over a period of time. This gas loss can occur when the electrodes 18,20 sputter-off metal atoms which can entrap neon gas atoms against the wall of a channel. Additionally, the electrodes can absorb some of the gas and neon gas can be diffused into the walls of the structure. Another modification that may be made, is that in some legends (such a legend is not shown in the figures) it is possible to create a connecting channel that connects two ends of an etched legend in lieu of a crossover channel 24b as shown in FIGURE 7. In this design, the connecting channel is cut into the upper side of the center plate 24 with the two ends abutting the ends of the legend. Thus, eliminating the need for the crossover bores 24c and the crossover channel 24b as shown in FIGURE 7. Hence, the invention is described to cover any and all modifications and forms which may come within the language and scope of the claims.

Claims: A luminous sign (10) comprising: a front transparent legend plate (12) having a legend (12a) consisting of a legend cavity that is formed in the back of the plate (12) where the legend (12a) has a beginning end (12d) and an ending end (12e) and the legend (12a) is interrupted at legend crossover intersections (12b); a center feedthrough plate (14) located behind the front transparent legend plate (12); a back plate (16) located behind the center feed through plate (14), the back plate having a first power/gas input bore (1Gb) and a second power/gas input bore (16c); means to hermetically bond (32) all of the plates (12, 14, 16) in the order indicated; means to insert (18, 18c) and hermetically encapsulate within the confines of the encapsulated legend cavities an optimum quantity of an ionizable gas; and means to activate (18d, 20c) the ionizable gas such that the gas causes a luminous radiation across the legend (12a) wherein: the center feedthrough plate (14) has a termination bore (14a) therethrough in alignment with the beginning end (12d) and the ending end (12e) of the legend (12a) and the crossover bore (14b) in alignment with each legend crossover point of every crossover intersection (12b); the back plate has a crossover cavity (16a) on its topside that extends over the area encompassing each of the legend crossover intersections (12b) on the front transparent legend plate (12) and across the respective crossover bore (14b) on the center feedthrough plate (14); each input bore (16b, 16c) of the back plate is in concentric alignment with each of the respective termination bores (14a) on the center feedthrough plate (14); characterized in that: means is provided to align all three of the plates (12, 14, 16) in the order indicated; and the means to hermetically bond all three of the plates (12, 14), 16) is accomplished by (a) selectively applying a temperature-sensitive adhesive to the contacting surface on each of the plates, (b) aligning the plates, (c) compressing the plates by a compression means, and (d) allowing the plates to cure under compression and temperature. A luminous sign (10) comprising: a front transparent legend plate (12) having a legend (12a) consisting of a legend cavity that is formed in the back of the plate (12) where the legend (12a) has a beginning end (12d) and an ending end (12e) and the legend (12a) is interrupted at legend crossover intersections (12b), a center plate (24) located behind the front transparent legend plate (12), a back feedthrough plate (26) located behind the center plate (24), the back feedthrough plate (26) having a first power/gas input bore (26a) and a second power/gas input bore (26b), means to hermetically bond (32) all of the plates (12, 24, 26) in the order indicated, means to insert (18, 18c) and hermetically encapsulate within the confines of the encapsulated legend cavities an optimum quantity of an ionizable gas, and means to activate (18d, 20c) the ionizable gas such that the gas causes a luminous radiation across the legend (12a) characterized in that: the center plate (24) has a crossover cavity (24b) on its backside that extends over the area encompassing each of the legend crossover intersections (12a) with each crossover cavity (24b) having two crossover bores (24c) where each of the bores (24c) is located within the cavity at each end and where the crossover bores (24c) extend upwardly interfacing with the ends of the applicable legend crossover point, and with the center plate (24) also having termination bores (24a) in alignment with the beginning (12d) and ending (12e) ends of the legend (12a); each input bore (26a, 26b) of the back feedthrough plate is in concentric alignment with each of the respective termination bores (24a) on the center plate (24); means is provided to align all three plates (12, 24, 26) in the order indicated. The luminous sign (10) according to Claim 2 characterized in that the means to hermetically bond all three of the plates (12, 24, 26) is accomplished by (a) selectively applying a temperature-sensitive adhesive to the contacting surface on each of the plates, (b) aligning the plates, (c) compressing the plates by a compression means, and (d) allowing the plates to cure under compression. The luminous sign (10) as claimed in Claims 1, 2 or 3 characterized in that the legend cavity is formed by a cavity producing means. The luminous sign (10) as claimed in Claims 1, 2 or 3 characterized in that the legend cavity is formed by molding the front transparent legend plate (12) over a mold incorporating the legend (12a). The luminous sign (10) as claimed in Claims 1, 2 or 3 further characterized by an opaque coating (12f) that is applied to the legend background area or the backside of the front transparent legend plate (12), where the opaque coating (12f) permits light to be transmitted only through the legend (12a). The luminous sign (10) as claimed in Claim 5 characterized in that the legend background area is coated with a legend-contrasting color (12g). The luminous sign (10) as claimed in Claim 5 characterized in that the opaque coating (12f) is applied prior to forming the legend cavity. The luminous sign (10) as claimed in Claims 1,2 or3 further characterized by a color selectable phosphorescent chemical (12g) that is applied to the legend cavity surface, where the phosphorescent chemical (12g) allows the legend (12a) to radiate in selectable colors. The luminous sign (10) as claimed in Claim 8 characterized in that a plurality of different phosphorescent chemicals (12g) are applied to the legend cavity surface at selected intervals so that the legend (12a) illuminates in a plurality of colors. The luminous sign (10) as claimed in Claims 1, 2 or 3 characterized in that the means to align all three of the plates (12, 14, 16; 12, 24, 26) is accomplished by precisely cutting on each of the plates (12, 14, 16; 12, 24, 26) two adjacent edges that form an angle where the edges of the angle serve as registration edges. The luminous sign (10) as claimed in Claims 1, 2 or 3 characterized in that the means to hermetically bond (32) all three of the plates (12, 14, 16; 12, 24, 26) is accomplished by applying a gasket (36) of insulation material on the top and bottom surfaces of the center plates (14, 24). The luminous sign as claimed in Claims 1, 2 or 3 characterized in that the means to insert (18, 18c) and hermetically encapsulate within the confines of the encapsulated legend cavities an optimum quantity of ionizable gas is accomplished by a) inserting and hermetically sealing a tubulated electrode (18) into the first power/gas input bore (16b, 26a), b) inserting and hermetically sealing a nontubulated electrode (20) into the second power/gas input bore (16c, 26b), c) applying and maintaining a vacuum to the tubulated section of the tubulated electrode (18) while the sign (10) is at an elevated temperature, d) inserting the ionizing gas through tubulated section of the tubulated electrode (18), and e) heating the tubulation to a molten state to cause the partial pressure within the tubulated electrode (18) to draw the molten tube walls inwardly to create a seal. The luminous sign (10) as claimed in Claims 1, 2 or 3 characterized in that the means to ionize the gas is accomplished by applying an electrical current across the electrodes (18, 20) on the tubulated electrode and nontubulated electrode. The luminous sign (10) as claimed in Claims 1, 2 or 3further characterized by a reservoir cavity (25) cut into one of the plates of the luminous sign (10) where the reservoir cavity (25) is placed away from the etched legend (12a) and is connected into a circuit channel by means of a narrow feeder channel.

Inventors: GARJIAN MICHAEL, GARJIAN, MICHAEL
Applicants: GARJIAN MICHAEL, GARJIAN, MICHAEL
Application year: 1987
Main classification: G09F13
IPC codes: G09F17, G09F13