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Patent US4725298 - Method for making low pressure mercury vapor discharge lamp - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA low pressure mercury vapor discharge lamp forms an electric discharge path by the use of a bulb placed on an end plate and the bulb is formed by a process which results in the connecting outer side surfaces of juxtaposed glass tubes through communication holes formed in the outer side surfaces respectively....http://www.google.com/patents/US4725298?utm_source=gb-gplus-sharePatent US4725298 - Method for making low pressure mercury vapor discharge lampAdvanced Patent SearchPublication numberUS4725298 APublication typeGrantApplication numberUS 06/861,724Publication dateFeb 16, 1988Filing dateMay 12, 1986Priority dateAug 12, 1983Fee statusPaidAlso published asCA1250886A1, DE3483829D1, EP0151647A1, EP0151647A4, EP0151647B1, US4703227, US4840593, WO1985000926A1Publication number06861724, 861724, US 4725298 A, US 4725298A, US-A-4725298, US4725298 A, US4725298AInventorsTakao Takeda, Hitoshi Yamazaki, Yoshiteru Taniguchi, Norihiko Tanaka, Hiroshi Ito, Minoru Uchida, Jun ImaiOriginal AssigneeMitsubishi Denki Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (4), Referenced by (1), Classifications (15), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetMethod for making low pressure mercury vapor discharge lamp
US 4725298 AAbstract
A low pressure mercury vapor discharge lamp forms an electric discharge path by the use of a bulb placed on an end plate and the bulb is formed by a process which results in the connecting outer side surfaces of juxtaposed glass tubes through communication holes formed in the outer side surfaces respectively. The process involves placing the juxtaposed glass tubes so that their outer surfaces are opposed in a contacting state. A portion of each of the glass tubes is heated in order to form a communication hole through the utilization of a burner inserted through an open end into the interior of each of the glass tubes in order to cause fusion of that particular portion in each tube to thereby form the communication hole by wind pressure. A mass of molten glass is then forced outward at the outer peripheral edge of the communication hole whereby these outer peripheral edges of the glass tubes are mutually connected by the mass of molten glass and the open end of the tubes are then closed to form a U-shaped passage between the tubes.
1. A process for preparing a low pressure mercury vapor discharge lamp for forming an electric discharge path by a bulb placed on an end plate, wherein said bulb is formed by connecting outer side surfaces of juxtaposed glass tubes through communication holes formed in said outer side surfaces while keeping air-tightness with respect to the atmosphere, wherein said bulb forming comprises the steps of:placing said juxtaposed glass tubes so that said outer side surfaces are opposed to each other in a contacting state; heating a portion of each of said glass tubes in order to form a communciation hole wherein said heating is accomplished by a flame of a burner inserted through an open end into the interior of each of said glass tubes in order to cause fusion of said portions to thereby form said communication hole by wind pressure of said burners; and forcing outward a mass of molten glass at the outer peripheral edge of said communication hole whereby said outer peripheral edges of said juxtaposed glass tubes are mutually connected by said mass of molten glass closing said open end of said tubes to form a U-shaped passage between the tubes. 2. A process for preparing a low pressure mercury vapor discharge lamp according to claim 1, wherein each one end part of said juxtaposed glass tubes is closed.
3. A process for preparing a low pressure mercury vapor discharge lamp according to claim 1, wherein said juxtaposed glass tubes are formed in a U-shape.
4. A process for preparing a low pressure mercury vapor discharge lamp for forming an electric discharge path by a bulb placed on an end plate, wherein said bulb is formed by contacting outer side surfaces of juxtaposed glass tubes through communication holes formed in said outer side surfaces while keeping air-tightness with respect to the atmosphere, wherein said bulb forming comprises the steps of:placing said outer side surfaces of said juxtaposed glass tubes so that both end parts are opened and so that said outer side surfaces are opposed to each other in a contacting state; heating by a flame of a burner inserted into the interior of each one of said glass tubes to cause fusion of a portion of each tube wherein said portions are opened to form a communication hole between said tubes which is near the end part to thereby form a communciation hole by wind pressure of said burners; forcing outward a mass of molten glass at the outer peripheral edge of said communciation hole whereby the outer peripheral edges of said juxtaposed glass tubes are mutually connected by said mass of molten glass; and heating the end parts at the side of said communciation holes of said glass tubes in order to cause melt-bonding due to shrinkage in the end parts; and placing said melt-bonding portion of said glass tubes in a mold having a predetermined shape and applying a pressure to the inside of said glass tubes to shape said melt-bonding portion. Description
This is a division of application Ser. No. 723,967, filed Apr. 12, 1985.
The present invention relates to a low pressure mercury vapor discharge lamp provided with a bulb for forming an electric discharging path and preparation thereof.
There has been known a fluorescent lamp such as a low pressure mercury vapor discharge lamp provided with a U-shaped bulb formed with bending or connecting processes, from a publication such as Japanese Unexamined Patent Publication No. 155675/1979 (FIG. 1) or Japanese Unexamined Patent Publication No. 133744/1980 (FIG. 2). The fluorescent lamp having such construction is advantageous because a lamp is made in a compact form. However, the U-shaped bulb 1 as shown in the figure has a space of gap 31 between both legs 1a, 1b. Therefore, in manufacturing steps, when the legs 1a, 1b of the bulb 1 are gripped from their outer sides so that a force is applied in its central direction, a connecting part 2a between the both legs 1a, 1b is apt to cause breakage. Accordingly, a device A is generally used to grip the both legs 1a, 1b of the bulb 1 in a plan passing through the legs 1a, 1b, as shown in FIG. 3 which is disclosed in Japanese Unexamined Patent Publication No. 124928/1980. On the other hand, the fluorescent lamp in a compact form which is substituted for an incandescent lamp generally has the legs 1a, 1b of the bulb 1 of about 100-150 mm in height, on account of which the bulb has to be supported in only one direction in the manufacturing steps. This means that it is necessary to prepare the device A used for various manufacturing steps at a high accuracy thereby to cause problems of complicated maintenance and inspection.
Further, there has been proposed a fluorescent lamp in which a U-shaped bulb 1 is further bent into two parts (hereinbelow referred to as a double U-shaped bulb) aiming at further compactness of the lamp. FIG. 4 shows a lamp, as an example, disclosed in Japanese Unexamined Patent Publication No. 108162/1980. In this case, two U-shaped bulbs 1, 1 are arranged so that there remain spaces of gap 31, 32, 33 and 34 between all adjoining legs among the legs 1a, 1b, 1c and 1d. Therefore, when the two U-shaped bulbs have to be supported by a supporting device A without causing breakage of the connecting parts 2a, 2b, the structure of the device A must be complicated in comparison with the device for a single U-shaped bulb 1, this prohibiting a large scale production. The same condition applys to a fluorescent lamp of a double tube structure in which a U-shaped bulb is placed inside an outer bulb.
The present invention has been attained in view of the above-mentioned circumstances and it is an object of the present invention to provide a low pressure mercury vapor discharge lamp enabling a bulb to be easily gripped by a supporting device in manufacturing steps, simplifying a manufacturing device, rendering maintenance and inspection to be easy and allowing a large scale poduction, by arranging legs of a U-shaped bulb in a contacting state.
It is further object of the present invention to provide a low pressure mercury vapor discharge lamp which is withstands an external force without pushing up manufacturing cost and impairing productivity and improves reliability on a bonding part by connecting a plurality of U-shaped glass bulbs in series, bonding both ends of the U-shaped glass bulbs directly to a common end plate with an adhesive and projecting electrodes so as to extend from the end plate inside the both ends of the glass bulb connected in series.
It is another object of the present invention to provide a process for preparing a low pressure merecury vapor discharge lamp which improves, in particular, coating operations of glass frit, assembling of parts and melting and solidifying operations of the glass frit when the bottom of a bulb, a stem and a discharge tube are bonded to an end plate through glass frit and which makes application of automatical operation easy and improved lamp characteristic.
FIGS. 1 and 2 are respectively front views of conventional U-shaped fluorescent lamps;
FIGS. 13 to 16 are respectively enlarged cross-sectional view of the other embodiments of the present invention;
FIG. 5 is a front view partly omitted on an embodiment of the U-shaped fluorescent lamp according to the present invention. In FIG. 5, a reference numeral 1 designates a U-shaped bulb formed by juxtaposing two linear tubes of soda-line glass of 16.5 mm in outer diameter and 0.8 mm thick and connecting each one end so that the interior of the tubes is communicated with each other while keeping air-tightness to the outside. The heightness of thus obtained bulb 1 is 140 mm. Both the legs 1a, 1b of the bulb 1 are substantially in close contact with each other to constitute a contacting state. The contacting state referred in the specification means that a space of gap 31 between the end part 1a' of the leg 1a and the end part 1b' of the leg 1b of the bulb 1 is in the range of 0-0.8 mm. In other words, in the U-shaped bulb, when a force is applied to both the end parts 1a', 1b' toward the gap 31 from the outside, namely, when a force is applied to the both legs 1a, 1b from the side of plane perpendicular to a plane passing between the legs 1a, 1b, a tensile stress is applied to the connecting part 2a of the bulb 1 to cause elastic deformation in the connecting part 2a. However, since the both end parts 1a', 1b' of the legs are brought into a contacting state in the range not to exceed limitation of the elastic deformation breakage of the connecting part 2a is prevented. A reference numeral 4 designates fluorescent layer, a numeral 5 designates 5 a stem, a numeral 6 designates electrodes, a numeral 7 designates a base metal, a numeral 8 designates a base metal pin, a numeral 9 designates an adhesive and a numeral 10 designates an end plate, all of which are the same as those used in the conventional lamp as shown in FIGS. 1 to 4.
In the fluorescent lamp constructed as above-mentioned, the both legs 1a, 1b of the bulb 1 are brought into a contacting state before the connecting part 2a exceeds limitation of the elastic deformation even though the elastic deformation is resulted in the connecting part 2a by a force applied to the both legs 1a, 1b toward the central part of them. Accordingly, the contacting part can resist against an external force applied after the legs have been contacted with each other to thereby avoid breakage of the connecting part 2a. The construction of the embodiment utilizes property of glass that it withstands compression stress although glass is apt to break against tensile stress. Therefore, there is no particular restriction to a manner of gripping the bulb 1 in manufacturing of the lamp whereby the structure of a manufacturing device is simplified and handling operations for bulbs in manufacturing steps can be flexible. However, when the gap 31 between the end parts 1a', 1b' of the legs 1a, 1b exceeds 0.8 mm in the above-mentioned embodiment, there greatly increase breakage of connecting part 2a. Naturally, dimension of the gap 31 is variable depending on the thickness of glass constituting the bulb 1 and the height of the bulb 1. When the outer configuration of the bulb 1 corresponds to a known incandescent lamp as is in the above-mentioned embodiment, it is effective to determine the gap 31 in the range of 0-0.8 mm, as stated above.
FIGS. 6 to 8 show another embodiment of the present invention in which FIG. 6 is a perspective view, FIG. 7 is a developed view and FIG. 8 is a plan view. In these Figures, numerals 1, 1 designate two U-shaped glass tubes, each being similar to that as shown in FIG. 5, in which they are integrally connected through a connecting part 2b which connects each one leg 1b, 1d of the both tubes so as to keep air-tightness to the atmosphere. The outer dimension of the U-shaped glass tubes is the same as that of FIG. 5 provided that the height of the tubes is 92 mm. In the bulb 1 formed by integrally connecting two U-shaped tubes, the end parts 1a', 1b', 1c' and 1d' of the legs are sealingly bonded to a disc-like ceramic end plate 10 with an adhesive of glass frit. Further, the legs 1a, 1b of the bulb 1 and the legs 1c, 1d of the other bulb 1 are firmly connected to the end plate 10 in such a manner that the legs 1a, 1c and the legs 1b, 1d which are respectively ones of adjacent bulbs 1, 1, are opposed in a contacting state. Namely, gaps 31, 32, 33, 34 of mutually adjoining legs 1a, 1b, 1c, 1d are espectively in the range of 0-0.8 mm.
The fluorescent lamp having the construction as above-mentioned allows easiness of gripping of it in manufacturing steps, in addition that after completion of assemblage, breakage of the bulb 1 which may be caused when the lamp is attached to or detached from a lamp socket (not shown) is effectively prevented. Generally, in case of attaching or detaching operation of a lamp of this kind, the bulb 1 is gripped by an operator and a torque is applied to the bulb 1. Accordingly, in the attaching or detaching operation of the lamp, a torque and a force bringing the U-shaped glass tubes in contact with each other are centralized to the leg end parts 1a'-1d' of the bulb 1 whereby breakage of the leg end parts 1a'-1d' often takes place. However, in the embodiment of the lamp having four legs 1a-1d each being in contacting state, the legs 1a-1d can sufficiently withstand an external force which causes the legs to come in mutual contact. Further, because all the leg end parts 1a'-1d' are firmly connected to the end plate, the torque applied to the leg end parts 1a'-1d' is dispersed to reduce a risk of the breakage. In addition, this embodiment can be further in a compact form while elongate a discharge path and lamp efficiency can be further improved.
In the embodiment shown in FIGS. 6-8, however, all of the leg end parts 1a'-1d' of the serially connected bulb 1 are in contact with a single common end plate 10 and are sealingly bonded with the adhesive 11 of glass frit. Accordingly, each of the leg end parts 1a'-1d' cooperates to resist against an external force to fall down the bulb 1 if such external force is applied to the bulb 1. Accordingly, a trouble that there takes place cracks in the adhesive 11 of glass frit in the bonding part to break air-tightness in the bulb 1, owing to a force to fall down the bulb, can be eliminated. On the other hand, since the bulb 1 is so constructed that the legs 1a-1d are arranged in a bundled condition as shown in FIG. 6, it is unnecessary to provide an auxiliary means to support the bulb 1 in order to prevent the bulb 1 from falling down even at the time of solidifying operations of the adhesive 11 of glass frit, whereby the manufacturing steps for the lamp can be remarkably simplified.
A structure for preventing falling down of the bulb 1 is disclosed, for example, in Japanese Patent Aplication No. 213158/1982 which shows a lamp having a double tube structure. In such lamp, when legs of the bulb are gathered and when the glass bulb and an outer bulb are connected to a common end plate with use of glass frit, the glass bulb, the outer bulb and a glass stem can be simultaneously attached and solidified since the glass bulb can stand itself. Industrial merit obtained by such structure is great. The glass bulb shown in Japanese Patent Application No. 213158/1982 is formed in a double U-shape and the leg end portion at the side without receiving therein an electrode constitutes a curved portion which corresponds to the connecting part of this embodiment. In connecting the U-shaped glass bulbs, there is no limitation to use two U-shaped glass bulbs as in this embodiment but it may use more than two number of U-shaped glass bulbs with both legs which contain no electrode. In this case, when more than two number of U-shaped glass bulbs are arranged on the end plate so as to represent a polygon, it can impart an excellent design.
The fluorescent lamp having the double tube structure as above-mentioned forms, in one hand, a double U-shaped electric discharge path as similar to the embodiment shown in FIGS. 6 to 8 and, on the other hand, causes the outer bulb 13 to form the mostly cooled part, whereby a mercury vapor pressure in the electric discharge space can be properly maintained to increase lamp efficiency. In this embodiment, since bulbs 1, 1 are arranged in mutually contacting state, the outer configuration of the lamp can be in a compact form in comparison with the conventional lamp having a double tube structure. Further, since the lamp is so made that any external force is not applied to the bulbs after completion of assembleage, it is sufficient to bond only the leg end parts 1a', 1c' receiving therein electrodes 6 to the end plate 10 with the adhesive 11 of glass frit. Accordingly, simplification of the manufacturing steps can be performed without reducing strength of the lamp required at the time of attaching or detaching operation. In addition, the lamp is of a structure that when the bulbs 1, 1 are bonded to the end plate 10, the leg end parts 1a'-1d' formed integrally with each other by means of connecting parts 2a, 2b, 2a are to be brought into contact with the end plate 10. Accordingly, bonding operation can be satisfactorily conducted without requirement of any auxiliary means to support the bulbs 1, 1.
With the construction as above-mentioned, the inner walls 1a'1, 1b'1 of the opened leg end parts 1a', 1b' of the bulb block prevent the molten adhesive from leaking out the outer circumferential edges of the opened leg end parts 1a', 1b'. Further, the adhesive 11 of glass frit is applied to have a form of ring the diameter of which is more or less smaller than the inner diameter of the opened leg end parts 1a', 1b' of the bulb and accordingly, an amount of the adhesive to be applied can be reduced even if the adhesive is coated thicker, in comparison with a case that the end surfaces 1a'3, 1b'3 of the opened leg end parts 1a', 1b' of the bulb are placed on the end plate 10 on which the adhesive 11 of glass frit is previously applied. A bulb 1 of 15 mm in inner diameter at open end and of 0.85 mm thick was prepared to compare an amount of the adhesive to be applied for this embodiment with the case in which the adhesive was previously applied. It revealed that the amount of the adhesive for this embodiment is about 2.5 g for one lamp whereas 4.5 g for the other case. Further, air-tightness between the atmosphere and the bulb 1 of the open leg end parts 1a', 1b'. In this case, since the inner walls 1a'1, 1b'1 are not contaminated with dust in comparison with the outer walls 1a'2, 1b'2, there takes place no problem of air-tightness. In addition, since the length of the circle of the inner walls 1a'1, 1b'1 is shorter than that the outer walls 1a'2, 1b'2, area for air-tightness is small. It is, therefore, advantageous in maintaining air-tightness. Further, the opened leg end parts 1a', 1b' are mounted on the end plate having a flat surface whereby there is no risk of causing inclination of the bulb.
In the above-mentioned embodiments, description has been made as to lamps having U-shaped bulb. It is, however, not limited to a U-shape and it can be a shape as shown in FIG. 17. The bulb of the embodiments as above-mentioned can be applicable to a lamp having a double tube structure shown in FIG. 18 in which a bulb in a curbed form is arranged in a outer bulb 13 which provides a sealing space.
In the lamp of this embodiment, both the leg end parts 1a', 1b' of the bulb 1 are firmly connected into a single common fitting groove 10a formed in the end plate 10. Accordingly, application of the adhesive 11 of glass frit to the fitting position groove 10a is carried out by squeezing out glass frit paste in a letter of 8; thus, a single continuous squeezing operation of the glass frit paste is satisfactory to coat the paste in the fitting groove 10a. A single fitting groove structure of the embodiment greatly reduces time for applying the glass frit paste in comparison with a structure in which fitting grooves are separately formed. Namely, in the single fitting groove structure, it is unnecessary to squeeze the glass frit into one fitting groove after having stopped the squeezing operation to a separate fitting groove, in other wards, it is unnecessary to repeat operations of dispense and stop.
Another embodiment of the present invention will be descrived with reference to FIGS. 28 to 32. In these Figures, a reference numeral 1 designates a bulb consisting of two U-shaped glass tubes 1a, 1d made of soda-lime glass in which each one leg 1b', 1d' of the glass tubes is communicated with each other while keeping air tightness to the atmosphere and leg end parts 1b', 1d' of the bulbs are opened. A numeral 10 designates an end plate made of forsterite ceramics which is square in shape and sealingly closes the opened leg end parts 1a'-1d' of the bulb 1. In the upper surface of the end plate 10, grooves 10a-10d respectively receiving therein the opened leg-end parts 1a', 1d' of the bulb 1, stem inserting holes 10h for receiving stems, described below, which are respectively formed in the grooves 10a, 10c and an exhaust tube insertion hole 10j which is formed in one of the grooves 10a, are provided. The grooves 10a, 10c are adapted to receive the stems.
Numerals 61 designate flared stems made of lead glass in which electrodes 6 are respectively sealingly attached and lead wires 62 and glass fine tubes 63 respectively extend outside from the stems. The diamter of a flared portion of the stems 61 is slightly smaller than the inner diameter of the glass tubes 1a, 1c of the bulb 1. A numeral 14 designates an exhaust tube made of lead glass. A flange-like enlarged diameter part 4b having a diameter greater than the exhaust tube insertion holes 10j is formed near the top end 14a of the exhaust tube 6 which is inserted in the bulb 1. A numeral 15 designates a pellet in a ring shape which is formed by molding glass frit as described below. A numeral 2b designates a connecting part for the bulbs 1b, 1d, and a numeral 4 designates a fluorescent layer coated on the inner surface of the bulb 1.
1. A glass frit 11 in past form is previously prepared by mixing glass frit powder consisting of lead borate as a main component (such as IWF-T029 (tradename) manufactured by Iwaki Glass K.K. and a vehicle (obtained by dissolving nitrocellulose in isoamyl acetate).
6. After completion of assembling operations, assembled products are put into a tunnel type furnace C as shown in FIG. 32 to be heated at 450� C. for 5 minutes whereby the adhesive 11 of glass frit and the pellets 5 as glass frit are molten heat and solidified; thus a series of bonding operations is completed.
On the other hand, when the exhaust tube 14, the pellet 5, the stems 61, and the bulb 1 are to be fitted to the end plate 1b in assembling operations, they are merely mounted or inserted in this order at given positions of the end plate as a series of operations which is easily carried out. The bonding of all parts can be performed by single heating step whereby the bonding step is simplified and there is no problem of reduction in strength in bonded portions.
In the above-mentioned embodiment, although description has been made as to bonding operation of a single bulb 1, the bonding operation of this embodiment can be applied to a lamp having a double tube structure comprising a first U-shaped bulb 1 and an outer bulb 13 as a second bulb which sealingly surround the first bulb 1, as shown in FIG. 34. Namely, in the lamp shown in FIG. 34, an annular groove 10i for receiving the bottom portion 13a of the outer bulb 13 and the second bulb is formed in the end plate 10 and the glass frit 11 is applied to the annular groove 10i at the same time of application of it to the grooves 10a-10d of the first bulb 1. In assembling operations, the outer bulb 13 as the second bulb may be mounted immediately after the first bulb 1 is mounted on the end plate. In the lamp in FIG. 34, an electric discharging space is formed by the second bulb, i.e. the outer bulb 13 and the end plate 10, on account of which it is not always necessary to form the insertion hole 10j for the exhaust tube 14 in the groove 10a or 10d, but the insertion hole 10j may be formed in a desired portion. A notched portion 1e is formed in the bulb 1 to communicate an enclosed gas between the bulb 1 and the outer bulb 13.
5. Around the connecting part and the jointed end part, now softened, of the glass tubes 100, 110, a splittable shaping mold 900 is applied as shown in FIG. 40, the splittable mold being provided with in its cavity a curved groove 910 as shown in FIG. 43. As soon as applying the splittable mold around the above-mentioned portions, air feeding nozzles 800 are put in end parts at the opposite side of the softened end part of the glass tubes 100, 110 to feed air in the glass tubes 100, 110 to thereby pressurize inside the glass tubes. The air of feeding operations cause expansion of the softened glass portions to be closely fitted to the groove 910 inside the mold 900.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS2561859 *Nov 3, 1949Jul 24, 1951Gen ElectricMethod of shaping vitreous tubesUS2699014 *Apr 23, 1953Jan 11, 1955Hartford Nat Bank & Trust CoMethod of manufacturing cathode-ray tubes comprising a glass cone and a glass windowUS4530710 *Oct 24, 1983Jul 23, 1985Gte Products CorporationLow-pressure arc discharge lamp having parallel discharge tubes with an arc-containing interconnecting channel; and method of manufacturing sameUS4545774 *Nov 28, 1983Oct 8, 1985U.S. Philips CorporationMethod of manufacturing a low-pressure mercury vapor discharge lamp and low-pressure mercury vapor discharge lamp manufactured by this method* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS6568217 *Sep 4, 2001May 27, 2003Matsushita Electric Industrial Co., Ltd.Method for manufacturing fluorescent lamp* Cited by examinerClassifications U.S. Classification65/23, 445/26, 65/55, 65/42, 65/36, 445/22, 65/34, 65/58, 65/45International ClassificationH01J9/26, H01J61/32Cooperative ClassificationH01J61/327, H01J9/26European ClassificationH01J61/32C, H01J9/26Legal EventsDateCodeEventDescriptionAug 9, 1999FPAYFee paymentYear of fee payment: 12Aug 7, 1995FPAYFee paymentYear of fee payment: 8Aug 7, 1991FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services